{"id":"7ea3c934-b2e2-4d3d-b304-8991f0120506","name":"Reverse Linked List (pointer - Recursive)","description":"1. You are given a partially written LinkedList class.\r\n2. You are required to complete the body of reversePR and reversePRHelper functions. The functions are expected to reverse the linked list by using recursion and changing the \"next\" data member of nodes.\r\n3. Input and Output is managed for you. \r\n\r\nNote -> The online judge can't force you to write recursive function, nor can it check if you changed the \"next\" data member or not. But that is what the expectation is, the intention in to help you learn.","inputFormat":"Input is managed for you","outputFormat":"Output is managed for you","constraints":"1. Time complexity -&gt; O(n)\r\n2. Space complexity -&gt; O(n)","sampleCode":{"cpp":{"code":"#include <iostream>\n#include <bits/stdc++.h>\n\nusing namespace std;\n\n class Node\n {\n public:\n int data = 0;\n Node *next = nullptr;\n\n Node(int data)\n {\n this->data = data;\n }\n };\n\n\n\nclass linkedlist\n{\n \npublic:\n\n Node *head = nullptr;\n Node *tail = nullptr;\n int size = 0;\n\n //basic->============================================\n\n int size_()\n {\n return this->size;\n }\n\n bool isEmpty()\n {\n return this->size == 0;\n }\n\n string toString()\n {\n Node *curr = this->head;\n string sb = \"\";\n\n while (curr != nullptr)\n {\n sb += to_string(curr->data);\n if (curr->next != nullptr)\n sb += \" \";\n curr = curr->next;\n }\n return sb;\n }\n\n //add->===============================================\nprivate:\n void addFirstNode(Node *node)\n {\n if (this->head == nullptr)\n {\n this->head = node;\n this->tail = node;\n }\n else\n {\n node->next = this->head;\n this->head = node;\n }\n\n this->size++;\n }\n\npublic:\n void addFirst(int val)\n {\n Node *node = new Node(val);\n addFirstNode(node);\n }\n\npublic:\n void addLastNode(Node *node)\n {\n if (this->head == nullptr)\n {\n this->head = node;\n this->tail = node;\n }\n else\n {\n this->tail->next = node;\n this->tail = node;\n }\n\n this->size++;\n }\n\n void addLast(int val)\n {\n Node *node = new Node(val);\n addLastNode(node);\n }\n\n void addNodeAt(Node *node, int idx)\n {\n if (idx == 0)\n addFirstNode(node);\n else if (idx == this->size)\n addLastNode(node);\n else\n {\n Node *prev = getNodeAt(idx - 1);\n Node *curr = prev->next;\n\n prev->next = node;\n curr->next = node;\n\n this->size++;\n }\n }\n\n void addAt(int data, int idx)\n {\n if (idx < 0 || idx > this->size)\n {\n throw(\"invalidLocation: \" + to_string(idx));\n }\n\n Node *node = new Node(data);\n addNodeAt(node, idx);\n }\n\n //remove->============================================\n Node *removeFirstNode()\n {\n Node *node = this->head;\n if (this->size == 1)\n {\n this->head = nullptr;\n this->tail = nullptr;\n }\n else\n {\n this->head = this->head->next;\n node->next = nullptr;\n }\n\n this->size--;\n return node;\n }\n\n int removeFirst(int val)\n {\n if (this->size == 0)\n {\n throw(\"nullptrPointerException: -1\");\n }\n\n Node *node = removeFirstNode();\n int rv = node->data;\n delete node;\n return rv;\n }\n\n Node *removeLastNode()\n {\n Node *node = this->tail;\n if (this->size == 1)\n {\n this->head = nullptr;\n this->tail = nullptr;\n }\n else\n {\n Node *prev = getNodeAt(this->size - 2);\n this->tail = prev;\n prev->next = nullptr;\n }\n\n this->size--;\n return node;\n }\n\n int removeLast(int val)\n {\n if (this->size == 0)\n {\n throw(\"nullptrPointerException: -1\");\n }\n\n Node *node = new Node(val);\n int rv = node->data;\n delete node;\n return rv;\n }\n\n Node *removeNodeAt(int idx)\n {\n if (idx == 0)\n return removeFirstNode();\n else if (idx == this->size - 1)\n return removeLastNode();\n else\n {\n\n Node *prev = getNodeAt(idx - 1);\n Node *curr = prev->next;\n\n prev->next = curr->next;\n curr->next = nullptr;\n\n this->size--;\n return curr;\n }\n }\n\n int removeAt(int idx)\n {\n if (idx < 0 || idx >= this->size)\n {\n throw(\"invalidLocation: \" + idx);\n }\n\n Node *node = removeNodeAt(idx);\n int rv = node->data;\n delete node;\n return rv;\n }\n\n //get->================================================\n Node *getFirstNode()\n {\n return this->head;\n }\n\n int getFirst()\n {\n if (this->size == 0)\n {\n throw(\"nullptrPointerException: -1\");\n }\n\n Node *node = getFirstNode();\n return node->data;\n }\n\n Node *getLastNode()\n {\n return this->tail;\n }\n\n int getLast()\n {\n if (this->size == 0)\n {\n throw(\"nullptrPointerException\");\n }\n\n Node *node = getLastNode();\n return node->data;\n }\n\n Node *getNodeAt(int idx)\n {\n Node *curr = this->head;\n\n while (idx-- > 0)\n {\n curr = curr->next;\n }\n\n return curr;\n }\n\n int getAt(int idx)\n {\n if (idx < 0 || idx >= this->size)\n {\n throw(\"invalidLocation: \" + idx);\n }\n\n Node *node = getNodeAt(idx);\n return node->data;\n }\n \n private:\n void displayReversePointerRecHelper(Node* node){\n //write your code here\n }\n \n public:\n void displayReversePointerRec(){\n //write your code here \n }\n};\n\n \nlinkedlist makeList() {\n linkedlist l;\n int n1;\n cin >> n1;\n\n for (int i = 0; i < n1; i++) {\n int val;\n cin >> val;\n l.addLast(val);\n }\n return l;\n}\n\n\nint main()\n{\n linkedlist l = makeList();\n int a;\n cin >>a;\n int b;\n cin >>b;\n \n cout<<l.toString()<< endl;\n l.displayReversePointerRec();\n l.addLast(a);\n l.addFirst(b);\n cout<<l.toString()<< endl;\n\n return 0;\n}"},"java":{"code":"import java.io.*;\r\nimport java.util.*;\r\n\r\npublic class Main {\r\n public static class Node {\r\n int data;\r\n Node next;\r\n }\r\n\r\n public static class LinkedList {\r\n Node head;\r\n Node tail;\r\n int size;\r\n\r\n void addLast(int val) {\r\n Node temp = new Node();\r\n temp.data = val;\r\n temp.next = null;\r\n\r\n if (size == 0) {\r\n head = tail = temp;\r\n } else {\r\n tail.next = temp;\r\n tail = temp;\r\n }\r\n\r\n size++;\r\n }\r\n\r\n public int size() {\r\n return size;\r\n }\r\n\r\n public void display() {\r\n for (Node temp = head; temp != null; temp = temp.next) {\r\n System.out.print(temp.data + \" \");\r\n }\r\n System.out.println();\r\n }\r\n\r\n public void removeFirst() {\r\n if (size == 0) {\r\n System.out.println(\"List is empty\");\r\n } else if (size == 1) {\r\n head = tail = null;\r\n size = 0;\r\n } else {\r\n head = head.next;\r\n size--;\r\n }\r\n }\r\n\r\n public int getFirst() {\r\n if (size == 0) {\r\n System.out.println(\"List is empty\");\r\n return -1;\r\n } else {\r\n return head.data;\r\n }\r\n }\r\n\r\n public int getLast() {\r\n if (size == 0) {\r\n System.out.println(\"List is empty\");\r\n return -1;\r\n } else {\r\n return tail.data;\r\n }\r\n }\r\n\r\n public int getAt(int idx) {\r\n if (size == 0) {\r\n System.out.println(\"List is empty\");\r\n return -1;\r\n } else if (idx < 0 || idx >= size) {\r\n System.out.println(\"Invalid arguments\");\r\n return -1;\r\n } else {\r\n Node temp = head;\r\n for (int i = 0; i < idx; i++) {\r\n temp = temp.next;\r\n }\r\n return temp.data;\r\n }\r\n }\r\n\r\n public void addFirst(int val) {\r\n Node temp = new Node();\r\n temp.data = val;\r\n temp.next = head;\r\n head = temp;\r\n\r\n if (size == 0) {\r\n tail = temp;\r\n }\r\n\r\n size++;\r\n }\r\n\r\n public void addAt(int idx, int val) {\r\n if (idx < 0 || idx > size) {\r\n System.out.println(\"Invalid arguments\");\r\n } else if (idx == 0) {\r\n addFirst(val);\r\n } else if (idx == size) {\r\n addLast(val);\r\n } else {\r\n Node node = new Node();\r\n node.data = val;\r\n\r\n Node temp = head;\r\n for (int i = 0; i < idx - 1; i++) {\r\n temp = temp.next;\r\n }\r\n node.next = temp.next;\r\n\r\n temp.next = node;\r\n size++;\r\n }\r\n }\r\n\r\n public void removeLast() {\r\n if (size == 0) {\r\n System.out.println(\"List is empty\");\r\n } else if (size == 1) {\r\n head = tail = null;\r\n size = 0;\r\n } else {\r\n Node temp = head;\r\n for (int i = 0; i < size - 2; i++) {\r\n temp = temp.next;\r\n }\r\n\r\n tail = temp;\r\n tail.next = null;\r\n size--;\r\n }\r\n }\r\n\r\n public void removeAt(int idx) {\r\n if (idx < 0 || idx >= size) {\r\n System.out.println(\"Invalid arguments\");\r\n } else if (idx == 0) {\r\n removeFirst();\r\n } else if (idx == size - 1) {\r\n removeLast();\r\n } else {\r\n Node temp = head;\r\n for (int i = 0; i < idx - 1; i++) {\r\n temp = temp.next;\r\n }\r\n\r\n temp.next = temp.next.next;\r\n size--;\r\n }\r\n }\r\n\r\n private Node getNodeAt(int idx) {\r\n Node temp = head;\r\n for (int i = 0; i < idx; i++) {\r\n temp = temp.next;\r\n }\r\n return temp;\r\n }\r\n\r\n public void reverseDI() {\r\n int li = 0;\r\n int ri = size - 1;\r\n while (li < ri) {\r\n Node left = getNodeAt(li);\r\n Node right = getNodeAt(ri);\r\n\r\n int temp = left.data;\r\n left.data = right.data;\r\n right.data = temp;\r\n\r\n li++;\r\n ri--;\r\n }\r\n }\r\n\r\n public void reversePI() {\r\n if (size <= 1) {\r\n return;\r\n }\r\n\r\n Node prev = null;\r\n Node curr = head;\r\n while (curr != null) {\r\n Node next = curr.next;\r\n\r\n curr.next = prev;\r\n prev = curr;\r\n curr = next;\r\n }\r\n\r\n Node temp = head;\r\n head = tail;\r\n tail = temp;\r\n }\r\n\r\n public int kthFromLast(int k) {\r\n Node slow = head;\r\n Node fast = head;\r\n for (int i = 0; i < k; i++) {\r\n fast = fast.next;\r\n }\r\n\r\n while (fast != tail) {\r\n slow = slow.next;\r\n fast = fast.next;\r\n }\r\n\r\n return slow.data;\r\n }\r\n\r\n public int mid() {\r\n Node f = head;\r\n Node s = head;\r\n\r\n while (f.next != null && f.next.next != null) {\r\n f = f.next.next;\r\n s = s.next;\r\n }\r\n\r\n return s.data;\r\n }\r\n\r\n public static LinkedList mergeTwoSortedLists(LinkedList l1, LinkedList l2) {\r\n LinkedList ml = new LinkedList();\r\n\r\n Node one = l1.head;\r\n Node two = l2.head;\r\n while (one != null && two != null) {\r\n if (one.data < two.data) {\r\n ml.addLast(one.data);\r\n one = one.next;\r\n } else {\r\n ml.addLast(two.data);\r\n two = two.next;\r\n }\r\n }\r\n\r\n while (one != null) {\r\n ml.addLast(one.data);\r\n one = one.next;\r\n }\r\n\r\n while (two != null) {\r\n ml.addLast(two.data);\r\n two = two.next;\r\n }\r\n\r\n return ml;\r\n }\r\n\r\n public static Node midNode(Node head, Node tail) {\r\n Node f = head;\r\n Node s = head;\r\n\r\n while (f != tail && f.next != tail) {\r\n f = f.next.next;\r\n s = s.next;\r\n }\r\n\r\n return s;\r\n }\r\n\r\n public static LinkedList mergeSort(Node head, Node tail) {\r\n if (head == tail) {\r\n LinkedList br = new LinkedList();\r\n br.addLast(head.data);\r\n return br;\r\n }\r\n\r\n Node mid = midNode(head, tail);\r\n LinkedList fsh = mergeSort(head, mid);\r\n LinkedList ssh = mergeSort(mid.next, tail);\r\n LinkedList sl = mergeTwoSortedLists(fsh, ssh);\r\n return sl;\r\n }\r\n\r\n public void removeDuplicates() {\r\n LinkedList res = new LinkedList();\r\n\r\n while (this.size() > 0) {\r\n int val = this.getFirst();\r\n this.removeFirst();\r\n\r\n if (res.size() == 0 || val != res.tail.data) {\r\n res.addLast(val);\r\n }\r\n }\r\n\r\n this.head = res.head;\r\n this.tail = res.tail;\r\n this.size = res.size;\r\n }\r\n\r\n public void oddEven() {\r\n LinkedList odd = new LinkedList();\r\n LinkedList even = new LinkedList();\r\n\r\n while (this.size > 0) {\r\n int val = this.getFirst();\r\n this.removeFirst();\r\n\r\n if (val % 2 == 0) {\r\n even.addLast(val);\r\n } else {\r\n odd.addLast(val);\r\n }\r\n }\r\n\r\n if (odd.size > 0 && even.size > 0) {\r\n odd.tail.next = even.head;\r\n\r\n this.head = odd.head;\r\n this.tail = even.tail;\r\n this.size = odd.size + even.size;\r\n } else if (odd.size > 0) {\r\n this.head = odd.head;\r\n this.tail = odd.tail;\r\n this.size = odd.size;\r\n } else if (even.size > 0) {\r\n this.head = even.head;\r\n this.tail = even.tail;\r\n this.size = even.size;\r\n }\r\n }\r\n\r\n public void kReverse(int k) {\r\n LinkedList prev = null;\r\n\r\n while (this.size > 0) {\r\n LinkedList curr = new LinkedList();\r\n\r\n if (this.size >= k) {\r\n for (int i = 0; i < k; i++) {\r\n int val = this.getFirst();\r\n this.removeFirst();\r\n curr.addFirst(val);\r\n }\r\n } else {\r\n int sz = this.size;\r\n for (int i = 0; i < sz; i++) {\r\n int val = this.getFirst();\r\n this.removeFirst();\r\n curr.addLast(val);\r\n }\r\n }\r\n\r\n if (prev == null) {\r\n prev = curr;\r\n } else {\r\n prev.tail.next = curr.head;\r\n prev.tail = curr.tail;\r\n prev.size += curr.size;\r\n }\r\n }\r\n\r\n this.head = prev.head;\r\n this.tail = prev.tail;\r\n this.size = prev.size;\r\n }\r\n\r\n private void displayReverseHelper(Node node){\r\n if(node == null){\r\n return;\r\n }\r\n displayReverseHelper(node.next);\r\n System.out.print(node.data + \" \");\r\n }\r\n\r\n public void displayReverse(){\r\n displayReverseHelper(head);\r\n System.out.println();\r\n }\r\n \r\n private void reversePRHelper(Node node){\r\n // write your code here\r\n }\r\n\r\n public void reversePR(){\r\n // write your code here\r\n }\r\n }\r\n\r\n public static void main(String[] args) throws Exception {\r\n BufferedReader br = new BufferedReader(new InputStreamReader(System.in));\r\n\r\n int n1 = Integer.parseInt(br.readLine());\r\n LinkedList l1 = new LinkedList();\r\n String[] values1 = br.readLine().split(\" \");\r\n for (int i = 0; i < n1; i++) {\r\n int d = Integer.parseInt(values1[i]);\r\n l1.addLast(d);\r\n }\r\n\r\n int a = Integer.parseInt(br.readLine());\r\n int b = Integer.parseInt(br.readLine());\r\n\r\n l1.display();\r\n l1.reversePR();\r\n l1.addLast(a);\r\n l1.addFirst(b);\r\n l1.display();\r\n }\r\n}"},"python":{"code":"class Node:\n\n def __init__(self):\n self.data = 0\n self.next = None\n\n\nclass LinkedList:\n\n def __init__(self):\n self.head = None\n self.tail = None\n self.size = 0\n\n#adding last in linkedlist\n\n def addLast(self, val):\n temp = Node()\n temp.data = val\n temp.next = None\n\n if self.size == 0:\n self.head = self.tail = temp\n else:\n self.tail.next = temp\n self.tail = temp\n\n self.size += 1\n \n#size of linkedlist\n\n def size(self):\n return self.size\n \n#display a linkedlist\n\n def display(self):\n temp = self.head\n while temp is not None:\n print(temp.data, end = \" \")\n temp = temp.next\n print()\n \n#remove first\n\n def removeFirst(self):\n if self.size == 0:\n print(\"List is empty\")\n elif self.size == 1:\n self.head = self.tail = None\n self.size = 0\n else:\n self.head = self.head.next\n self.size -= 1\n#get first\n\n def getFirst(self):\n if self.size == 0:\n print(\"List is empty\")\n return -1\n else:\n return self.head.data\n#get last \n\n def getLast(self):\n if self.size == 0:\n print(\"List is empty\")\n return -1\n else:\n return self.tail.data\n \n#getat in linkedlist\n\n def getAt(self, idx):\n if self.size == 0:\n print(\"List is empty\")\n return -1\n elif idx < 0 or idx >= self.size:\n print(\"Invalid arguments\")\n return -1\n else:\n temp = self.head\n i = 0\n while i < idx:\n temp = temp.next\n i += 1\n return temp.data\n\n# add first in linkedlist\n\n def addFirst(self, val):\n temp = Node()\n temp.data = val\n temp.next = self.head\n self.head = temp\n\n if self.size == 0:\n self.tail = temp\n\n self.size += 1\n\n# add at in linkedlist\n\n def addAt(self, idx, val):\n if idx < 0 or idx > size:\n print(\"Invalid arguments\")\n elif idx == 0:\n addFirst(val)\n elif idx == size:\n addLast(val)\n else:\n node = Node()\n node.data = val\n\n temp = head\n i = 0\n while i < idx - 1:\n temp = temp.next\n i += 1\n node.next = temp.next\n\n temp.next = node\n size += 1\n\n# remove last in linkedlist\n\n def removeLast(self):\n if size == 0:\n print(\"List is empty\")\n elif size == 1:\n head = tail = None\n size = 0\n else:\n temp = head\n i = 0\n while i < size - 2:\n temp = temp.next\n i += 1\n\n tail = temp\n tail.next = None\n size -= 1\n\n#remove at \n\n def removeAt(self, idx):\n if idx < 0 or idx >= size:\n print(\"Invalid arguments\")\n elif idx == 0:\n removeFirst()\n elif idx == size - 1:\n self.removeLast()\n else:\n temp = head\n i = 0\n while i < idx - 1:\n temp = temp.next\n i += 1\n\n temp.next = temp.next.next\n size -= 1\n\n#reverse pointer recursive\n\n def reversePRHelper(self, node):\n #write your code here\n\n def reversePR(self):\n #write your code here\n\n\n# input and output\n\nll = LinkedList()\n\nn = int(input())\nvalues = list(map(int,input().split(\" \")))\nfor i in range(n):\n ll.addLast(values[i])\n \na = int(input())\nb = int(input())\n\nll.display()\nll.reversePR()\nll.addLast(a)\nll.addFirst(b)\nll.display()"}},"points":10,"difficulty":"easy","sampleInput":"11\r\n1 2 3 4 5 6 7 8 9 10 11\r\n100\r\n200","sampleOutput":"1 2 3 4 5 6 7 8 9 10 11 \r\n200 11 10 9 8 7 6 5 4 3 2 1 100","questionVideo":"https://www.youtube.com/embed/Gj2y4GDLGf4","hints":[],"associated":[{"id":"2685ef70-8519-43b9-b17f-d78c68f25bca","name":"What is the time complexity of the given problem?(Q- RLPR)","slug":"what-is-the-time-complexity-of-the-given-problem-q-rlpr","type":4},{"id":"3be23126-8afb-4b29-a83c-033c4652d257","name":"Choose the correct syntax for making the calls to next node.(Q- RLPR)","slug":"choose-the-correct-syntax-for-making-the-calls-to-next-node-q-rlpr","type":4},{"id":"536548e9-d0e2-4bd6-abfe-8f6356da438f","name":"Is the original linked list changing?(Q- RLPR)","slug":"is-the-original-linked-list-changing-q-rlpr","type":4},{"id":"fc48da11-5c79-48dd-8ba0-da259d1ea55a","name":"In this problem, what are we making changes to?(Q- RLPR)","slug":"in-this-problem-what-are-we-making-changes-to-q-rlpr","type":4}],"solutionSeen":false,"tags":[],"meta":{"path":[{"id":0,"name":"home"},{"id":"0c54b191-7b99-4f2c-acb3-e7f2ec748b2a","name":"Data Structures and Algorithms","slug":"data-structures-and-algorithms","type":0},{"id":"91027ef1-2784-45bf-8143-cc6af4560105","name":"Linked Lists For Beginners","slug":"linked-lists-for-beginners","type":0},{"id":"14fe65a0-421f-4393-bd91-c63b9b82f8e2","name":"Reverse Linked List (pointer - Recursive)","slug":"reverse-linked-list-pointer-recursive","type":1}],"next":{"id":"2b1cbf91-87cc-4b36-8260-82c8129e5ef8","name":"Reverse Linked List Pointer Recursive","type":3,"slug":"reverse-linked-list-pointer-recursive"},"prev":{"id":"05da8aa3-c700-40f3-80b2-7b8e4906cee3","name":"Display Reverse (recursive) - Linked List","type":3,"slug":"display-reverse-recursive-linked-list"}}}

Reverse Linked List (pointer - Recursive)

1. You are given a partially written LinkedList class. 2. You are required to complete the body of reversePR and reversePRHelper functions. The functions are expected to reverse the linked list by using recursion and changing the "next" data member of nodes. 3. Input and Output is managed for you. Note -> The online judge can't force you to write recursive function, nor can it check if you changed the "next" data member or not. But that is what the expectation is, the intention in to help you learn.

{"id":"7ea3c934-b2e2-4d3d-b304-8991f0120506","name":"Reverse Linked List (pointer - Recursive)","description":"1. You are given a partially written LinkedList class.\r\n2. You are required to complete the body of reversePR and reversePRHelper functions. The functions are expected to reverse the linked list by using recursion and changing the \"next\" data member of nodes.\r\n3. Input and Output is managed for you. \r\n\r\nNote -> The online judge can't force you to write recursive function, nor can it check if you changed the \"next\" data member or not. But that is what the expectation is, the intention in to help you learn.","inputFormat":"Input is managed for you","outputFormat":"Output is managed for you","constraints":"1. Time complexity -&gt; O(n)\r\n2. Space complexity -&gt; O(n)","sampleCode":{"cpp":{"code":"#include <iostream>\n#include <bits/stdc++.h>\n\nusing namespace std;\n\n class Node\n {\n public:\n int data = 0;\n Node *next = nullptr;\n\n Node(int data)\n {\n this->data = data;\n }\n };\n\n\n\nclass linkedlist\n{\n \npublic:\n\n Node *head = nullptr;\n Node *tail = nullptr;\n int size = 0;\n\n //basic->============================================\n\n int size_()\n {\n return this->size;\n }\n\n bool isEmpty()\n {\n return this->size == 0;\n }\n\n string toString()\n {\n Node *curr = this->head;\n string sb = \"\";\n\n while (curr != nullptr)\n {\n sb += to_string(curr->data);\n if (curr->next != nullptr)\n sb += \" \";\n curr = curr->next;\n }\n return sb;\n }\n\n //add->===============================================\nprivate:\n void addFirstNode(Node *node)\n {\n if (this->head == nullptr)\n {\n this->head = node;\n this->tail = node;\n }\n else\n {\n node->next = this->head;\n this->head = node;\n }\n\n this->size++;\n }\n\npublic:\n void addFirst(int val)\n {\n Node *node = new Node(val);\n addFirstNode(node);\n }\n\npublic:\n void addLastNode(Node *node)\n {\n if (this->head == nullptr)\n {\n this->head = node;\n this->tail = node;\n }\n else\n {\n this->tail->next = node;\n this->tail = node;\n }\n\n this->size++;\n }\n\n void addLast(int val)\n {\n Node *node = new Node(val);\n addLastNode(node);\n }\n\n void addNodeAt(Node *node, int idx)\n {\n if (idx == 0)\n addFirstNode(node);\n else if (idx == this->size)\n addLastNode(node);\n else\n {\n Node *prev = getNodeAt(idx - 1);\n Node *curr = prev->next;\n\n prev->next = node;\n curr->next = node;\n\n this->size++;\n }\n }\n\n void addAt(int data, int idx)\n {\n if (idx < 0 || idx > this->size)\n {\n throw(\"invalidLocation: \" + to_string(idx));\n }\n\n Node *node = new Node(data);\n addNodeAt(node, idx);\n }\n\n //remove->============================================\n Node *removeFirstNode()\n {\n Node *node = this->head;\n if (this->size == 1)\n {\n this->head = nullptr;\n this->tail = nullptr;\n }\n else\n {\n this->head = this->head->next;\n node->next = nullptr;\n }\n\n this->size--;\n return node;\n }\n\n int removeFirst(int val)\n {\n if (this->size == 0)\n {\n throw(\"nullptrPointerException: -1\");\n }\n\n Node *node = removeFirstNode();\n int rv = node->data;\n delete node;\n return rv;\n }\n\n Node *removeLastNode()\n {\n Node *node = this->tail;\n if (this->size == 1)\n {\n this->head = nullptr;\n this->tail = nullptr;\n }\n else\n {\n Node *prev = getNodeAt(this->size - 2);\n this->tail = prev;\n prev->next = nullptr;\n }\n\n this->size--;\n return node;\n }\n\n int removeLast(int val)\n {\n if (this->size == 0)\n {\n throw(\"nullptrPointerException: -1\");\n }\n\n Node *node = new Node(val);\n int rv = node->data;\n delete node;\n return rv;\n }\n\n Node *removeNodeAt(int idx)\n {\n if (idx == 0)\n return removeFirstNode();\n else if (idx == this->size - 1)\n return removeLastNode();\n else\n {\n\n Node *prev = getNodeAt(idx - 1);\n Node *curr = prev->next;\n\n prev->next = curr->next;\n curr->next = nullptr;\n\n this->size--;\n return curr;\n }\n }\n\n int removeAt(int idx)\n {\n if (idx < 0 || idx >= this->size)\n {\n throw(\"invalidLocation: \" + idx);\n }\n\n Node *node = removeNodeAt(idx);\n int rv = node->data;\n delete node;\n return rv;\n }\n\n //get->================================================\n Node *getFirstNode()\n {\n return this->head;\n }\n\n int getFirst()\n {\n if (this->size == 0)\n {\n throw(\"nullptrPointerException: -1\");\n }\n\n Node *node = getFirstNode();\n return node->data;\n }\n\n Node *getLastNode()\n {\n return this->tail;\n }\n\n int getLast()\n {\n if (this->size == 0)\n {\n throw(\"nullptrPointerException\");\n }\n\n Node *node = getLastNode();\n return node->data;\n }\n\n Node *getNodeAt(int idx)\n {\n Node *curr = this->head;\n\n while (idx-- > 0)\n {\n curr = curr->next;\n }\n\n return curr;\n }\n\n int getAt(int idx)\n {\n if (idx < 0 || idx >= this->size)\n {\n throw(\"invalidLocation: \" + idx);\n }\n\n Node *node = getNodeAt(idx);\n return node->data;\n }\n \n private:\n void displayReversePointerRecHelper(Node* node){\n //write your code here\n }\n \n public:\n void displayReversePointerRec(){\n //write your code here \n }\n};\n\n \nlinkedlist makeList() {\n linkedlist l;\n int n1;\n cin >> n1;\n\n for (int i = 0; i < n1; i++) {\n int val;\n cin >> val;\n l.addLast(val);\n }\n return l;\n}\n\n\nint main()\n{\n linkedlist l = makeList();\n int a;\n cin >>a;\n int b;\n cin >>b;\n \n cout<<l.toString()<< endl;\n l.displayReversePointerRec();\n l.addLast(a);\n l.addFirst(b);\n cout<<l.toString()<< endl;\n\n return 0;\n}"},"java":{"code":"import java.io.*;\r\nimport java.util.*;\r\n\r\npublic class Main {\r\n public static class Node {\r\n int data;\r\n Node next;\r\n }\r\n\r\n public static class LinkedList {\r\n Node head;\r\n Node tail;\r\n int size;\r\n\r\n void addLast(int val) {\r\n Node temp = new Node();\r\n temp.data = val;\r\n temp.next = null;\r\n\r\n if (size == 0) {\r\n head = tail = temp;\r\n } else {\r\n tail.next = temp;\r\n tail = temp;\r\n }\r\n\r\n size++;\r\n }\r\n\r\n public int size() {\r\n return size;\r\n }\r\n\r\n public void display() {\r\n for (Node temp = head; temp != null; temp = temp.next) {\r\n System.out.print(temp.data + \" \");\r\n }\r\n System.out.println();\r\n }\r\n\r\n public void removeFirst() {\r\n if (size == 0) {\r\n System.out.println(\"List is empty\");\r\n } else if (size == 1) {\r\n head = tail = null;\r\n size = 0;\r\n } else {\r\n head = head.next;\r\n size--;\r\n }\r\n }\r\n\r\n public int getFirst() {\r\n if (size == 0) {\r\n System.out.println(\"List is empty\");\r\n return -1;\r\n } else {\r\n return head.data;\r\n }\r\n }\r\n\r\n public int getLast() {\r\n if (size == 0) {\r\n System.out.println(\"List is empty\");\r\n return -1;\r\n } else {\r\n return tail.data;\r\n }\r\n }\r\n\r\n public int getAt(int idx) {\r\n if (size == 0) {\r\n System.out.println(\"List is empty\");\r\n return -1;\r\n } else if (idx < 0 || idx >= size) {\r\n System.out.println(\"Invalid arguments\");\r\n return -1;\r\n } else {\r\n Node temp = head;\r\n for (int i = 0; i < idx; i++) {\r\n temp = temp.next;\r\n }\r\n return temp.data;\r\n }\r\n }\r\n\r\n public void addFirst(int val) {\r\n Node temp = new Node();\r\n temp.data = val;\r\n temp.next = head;\r\n head = temp;\r\n\r\n if (size == 0) {\r\n tail = temp;\r\n }\r\n\r\n size++;\r\n }\r\n\r\n public void addAt(int idx, int val) {\r\n if (idx < 0 || idx > size) {\r\n System.out.println(\"Invalid arguments\");\r\n } else if (idx == 0) {\r\n addFirst(val);\r\n } else if (idx == size) {\r\n addLast(val);\r\n } else {\r\n Node node = new Node();\r\n node.data = val;\r\n\r\n Node temp = head;\r\n for (int i = 0; i < idx - 1; i++) {\r\n temp = temp.next;\r\n }\r\n node.next = temp.next;\r\n\r\n temp.next = node;\r\n size++;\r\n }\r\n }\r\n\r\n public void removeLast() {\r\n if (size == 0) {\r\n System.out.println(\"List is empty\");\r\n } else if (size == 1) {\r\n head = tail = null;\r\n size = 0;\r\n } else {\r\n Node temp = head;\r\n for (int i = 0; i < size - 2; i++) {\r\n temp = temp.next;\r\n }\r\n\r\n tail = temp;\r\n tail.next = null;\r\n size--;\r\n }\r\n }\r\n\r\n public void removeAt(int idx) {\r\n if (idx < 0 || idx >= size) {\r\n System.out.println(\"Invalid arguments\");\r\n } else if (idx == 0) {\r\n removeFirst();\r\n } else if (idx == size - 1) {\r\n removeLast();\r\n } else {\r\n Node temp = head;\r\n for (int i = 0; i < idx - 1; i++) {\r\n temp = temp.next;\r\n }\r\n\r\n temp.next = temp.next.next;\r\n size--;\r\n }\r\n }\r\n\r\n private Node getNodeAt(int idx) {\r\n Node temp = head;\r\n for (int i = 0; i < idx; i++) {\r\n temp = temp.next;\r\n }\r\n return temp;\r\n }\r\n\r\n public void reverseDI() {\r\n int li = 0;\r\n int ri = size - 1;\r\n while (li < ri) {\r\n Node left = getNodeAt(li);\r\n Node right = getNodeAt(ri);\r\n\r\n int temp = left.data;\r\n left.data = right.data;\r\n right.data = temp;\r\n\r\n li++;\r\n ri--;\r\n }\r\n }\r\n\r\n public void reversePI() {\r\n if (size <= 1) {\r\n return;\r\n }\r\n\r\n Node prev = null;\r\n Node curr = head;\r\n while (curr != null) {\r\n Node next = curr.next;\r\n\r\n curr.next = prev;\r\n prev = curr;\r\n curr = next;\r\n }\r\n\r\n Node temp = head;\r\n head = tail;\r\n tail = temp;\r\n }\r\n\r\n public int kthFromLast(int k) {\r\n Node slow = head;\r\n Node fast = head;\r\n for (int i = 0; i < k; i++) {\r\n fast = fast.next;\r\n }\r\n\r\n while (fast != tail) {\r\n slow = slow.next;\r\n fast = fast.next;\r\n }\r\n\r\n return slow.data;\r\n }\r\n\r\n public int mid() {\r\n Node f = head;\r\n Node s = head;\r\n\r\n while (f.next != null && f.next.next != null) {\r\n f = f.next.next;\r\n s = s.next;\r\n }\r\n\r\n return s.data;\r\n }\r\n\r\n public static LinkedList mergeTwoSortedLists(LinkedList l1, LinkedList l2) {\r\n LinkedList ml = new LinkedList();\r\n\r\n Node one = l1.head;\r\n Node two = l2.head;\r\n while (one != null && two != null) {\r\n if (one.data < two.data) {\r\n ml.addLast(one.data);\r\n one = one.next;\r\n } else {\r\n ml.addLast(two.data);\r\n two = two.next;\r\n }\r\n }\r\n\r\n while (one != null) {\r\n ml.addLast(one.data);\r\n one = one.next;\r\n }\r\n\r\n while (two != null) {\r\n ml.addLast(two.data);\r\n two = two.next;\r\n }\r\n\r\n return ml;\r\n }\r\n\r\n public static Node midNode(Node head, Node tail) {\r\n Node f = head;\r\n Node s = head;\r\n\r\n while (f != tail && f.next != tail) {\r\n f = f.next.next;\r\n s = s.next;\r\n }\r\n\r\n return s;\r\n }\r\n\r\n public static LinkedList mergeSort(Node head, Node tail) {\r\n if (head == tail) {\r\n LinkedList br = new LinkedList();\r\n br.addLast(head.data);\r\n return br;\r\n }\r\n\r\n Node mid = midNode(head, tail);\r\n LinkedList fsh = mergeSort(head, mid);\r\n LinkedList ssh = mergeSort(mid.next, tail);\r\n LinkedList sl = mergeTwoSortedLists(fsh, ssh);\r\n return sl;\r\n }\r\n\r\n public void removeDuplicates() {\r\n LinkedList res = new LinkedList();\r\n\r\n while (this.size() > 0) {\r\n int val = this.getFirst();\r\n this.removeFirst();\r\n\r\n if (res.size() == 0 || val != res.tail.data) {\r\n res.addLast(val);\r\n }\r\n }\r\n\r\n this.head = res.head;\r\n this.tail = res.tail;\r\n this.size = res.size;\r\n }\r\n\r\n public void oddEven() {\r\n LinkedList odd = new LinkedList();\r\n LinkedList even = new LinkedList();\r\n\r\n while (this.size > 0) {\r\n int val = this.getFirst();\r\n this.removeFirst();\r\n\r\n if (val % 2 == 0) {\r\n even.addLast(val);\r\n } else {\r\n odd.addLast(val);\r\n }\r\n }\r\n\r\n if (odd.size > 0 && even.size > 0) {\r\n odd.tail.next = even.head;\r\n\r\n this.head = odd.head;\r\n this.tail = even.tail;\r\n this.size = odd.size + even.size;\r\n } else if (odd.size > 0) {\r\n this.head = odd.head;\r\n this.tail = odd.tail;\r\n this.size = odd.size;\r\n } else if (even.size > 0) {\r\n this.head = even.head;\r\n this.tail = even.tail;\r\n this.size = even.size;\r\n }\r\n }\r\n\r\n public void kReverse(int k) {\r\n LinkedList prev = null;\r\n\r\n while (this.size > 0) {\r\n LinkedList curr = new LinkedList();\r\n\r\n if (this.size >= k) {\r\n for (int i = 0; i < k; i++) {\r\n int val = this.getFirst();\r\n this.removeFirst();\r\n curr.addFirst(val);\r\n }\r\n } else {\r\n int sz = this.size;\r\n for (int i = 0; i < sz; i++) {\r\n int val = this.getFirst();\r\n this.removeFirst();\r\n curr.addLast(val);\r\n }\r\n }\r\n\r\n if (prev == null) {\r\n prev = curr;\r\n } else {\r\n prev.tail.next = curr.head;\r\n prev.tail = curr.tail;\r\n prev.size += curr.size;\r\n }\r\n }\r\n\r\n this.head = prev.head;\r\n this.tail = prev.tail;\r\n this.size = prev.size;\r\n }\r\n\r\n private void displayReverseHelper(Node node){\r\n if(node == null){\r\n return;\r\n }\r\n displayReverseHelper(node.next);\r\n System.out.print(node.data + \" \");\r\n }\r\n\r\n public void displayReverse(){\r\n displayReverseHelper(head);\r\n System.out.println();\r\n }\r\n \r\n private void reversePRHelper(Node node){\r\n // write your code here\r\n }\r\n\r\n public void reversePR(){\r\n // write your code here\r\n }\r\n }\r\n\r\n public static void main(String[] args) throws Exception {\r\n BufferedReader br = new BufferedReader(new InputStreamReader(System.in));\r\n\r\n int n1 = Integer.parseInt(br.readLine());\r\n LinkedList l1 = new LinkedList();\r\n String[] values1 = br.readLine().split(\" \");\r\n for (int i = 0; i < n1; i++) {\r\n int d = Integer.parseInt(values1[i]);\r\n l1.addLast(d);\r\n }\r\n\r\n int a = Integer.parseInt(br.readLine());\r\n int b = Integer.parseInt(br.readLine());\r\n\r\n l1.display();\r\n l1.reversePR();\r\n l1.addLast(a);\r\n l1.addFirst(b);\r\n l1.display();\r\n }\r\n}"},"python":{"code":"class Node:\n\n def __init__(self):\n self.data = 0\n self.next = None\n\n\nclass LinkedList:\n\n def __init__(self):\n self.head = None\n self.tail = None\n self.size = 0\n\n#adding last in linkedlist\n\n def addLast(self, val):\n temp = Node()\n temp.data = val\n temp.next = None\n\n if self.size == 0:\n self.head = self.tail = temp\n else:\n self.tail.next = temp\n self.tail = temp\n\n self.size += 1\n \n#size of linkedlist\n\n def size(self):\n return self.size\n \n#display a linkedlist\n\n def display(self):\n temp = self.head\n while temp is not None:\n print(temp.data, end = \" \")\n temp = temp.next\n print()\n \n#remove first\n\n def removeFirst(self):\n if self.size == 0:\n print(\"List is empty\")\n elif self.size == 1:\n self.head = self.tail = None\n self.size = 0\n else:\n self.head = self.head.next\n self.size -= 1\n#get first\n\n def getFirst(self):\n if self.size == 0:\n print(\"List is empty\")\n return -1\n else:\n return self.head.data\n#get last \n\n def getLast(self):\n if self.size == 0:\n print(\"List is empty\")\n return -1\n else:\n return self.tail.data\n \n#getat in linkedlist\n\n def getAt(self, idx):\n if self.size == 0:\n print(\"List is empty\")\n return -1\n elif idx < 0 or idx >= self.size:\n print(\"Invalid arguments\")\n return -1\n else:\n temp = self.head\n i = 0\n while i < idx:\n temp = temp.next\n i += 1\n return temp.data\n\n# add first in linkedlist\n\n def addFirst(self, val):\n temp = Node()\n temp.data = val\n temp.next = self.head\n self.head = temp\n\n if self.size == 0:\n self.tail = temp\n\n self.size += 1\n\n# add at in linkedlist\n\n def addAt(self, idx, val):\n if idx < 0 or idx > size:\n print(\"Invalid arguments\")\n elif idx == 0:\n addFirst(val)\n elif idx == size:\n addLast(val)\n else:\n node = Node()\n node.data = val\n\n temp = head\n i = 0\n while i < idx - 1:\n temp = temp.next\n i += 1\n node.next = temp.next\n\n temp.next = node\n size += 1\n\n# remove last in linkedlist\n\n def removeLast(self):\n if size == 0:\n print(\"List is empty\")\n elif size == 1:\n head = tail = None\n size = 0\n else:\n temp = head\n i = 0\n while i < size - 2:\n temp = temp.next\n i += 1\n\n tail = temp\n tail.next = None\n size -= 1\n\n#remove at \n\n def removeAt(self, idx):\n if idx < 0 or idx >= size:\n print(\"Invalid arguments\")\n elif idx == 0:\n removeFirst()\n elif idx == size - 1:\n self.removeLast()\n else:\n temp = head\n i = 0\n while i < idx - 1:\n temp = temp.next\n i += 1\n\n temp.next = temp.next.next\n size -= 1\n\n#reverse pointer recursive\n\n def reversePRHelper(self, node):\n #write your code here\n\n def reversePR(self):\n #write your code here\n\n\n# input and output\n\nll = LinkedList()\n\nn = int(input())\nvalues = list(map(int,input().split(\" \")))\nfor i in range(n):\n ll.addLast(values[i])\n \na = int(input())\nb = int(input())\n\nll.display()\nll.reversePR()\nll.addLast(a)\nll.addFirst(b)\nll.display()"}},"points":10,"difficulty":"easy","sampleInput":"11\r\n1 2 3 4 5 6 7 8 9 10 11\r\n100\r\n200","sampleOutput":"1 2 3 4 5 6 7 8 9 10 11 \r\n200 11 10 9 8 7 6 5 4 3 2 1 100","questionVideo":"https://www.youtube.com/embed/Gj2y4GDLGf4","hints":[],"associated":[{"id":"2685ef70-8519-43b9-b17f-d78c68f25bca","name":"What is the time complexity of the given problem?(Q- RLPR)","slug":"what-is-the-time-complexity-of-the-given-problem-q-rlpr","type":4},{"id":"3be23126-8afb-4b29-a83c-033c4652d257","name":"Choose the correct syntax for making the calls to next node.(Q- RLPR)","slug":"choose-the-correct-syntax-for-making-the-calls-to-next-node-q-rlpr","type":4},{"id":"536548e9-d0e2-4bd6-abfe-8f6356da438f","name":"Is the original linked list changing?(Q- RLPR)","slug":"is-the-original-linked-list-changing-q-rlpr","type":4},{"id":"fc48da11-5c79-48dd-8ba0-da259d1ea55a","name":"In this problem, what are we making changes to?(Q- RLPR)","slug":"in-this-problem-what-are-we-making-changes-to-q-rlpr","type":4}],"solutionSeen":false,"tags":[],"meta":{"path":[{"id":0,"name":"home"},{"id":"0c54b191-7b99-4f2c-acb3-e7f2ec748b2a","name":"Data Structures and Algorithms","slug":"data-structures-and-algorithms","type":0},{"id":"91027ef1-2784-45bf-8143-cc6af4560105","name":"Linked Lists For Beginners","slug":"linked-lists-for-beginners","type":0},{"id":"14fe65a0-421f-4393-bd91-c63b9b82f8e2","name":"Reverse Linked List (pointer - Recursive)","slug":"reverse-linked-list-pointer-recursive","type":1}],"next":{"id":"2b1cbf91-87cc-4b36-8260-82c8129e5ef8","name":"Reverse Linked List Pointer Recursive","type":3,"slug":"reverse-linked-list-pointer-recursive"},"prev":{"id":"05da8aa3-c700-40f3-80b2-7b8e4906cee3","name":"Display Reverse (recursive) - Linked List","type":3,"slug":"display-reverse-recursive-linked-list"}}}
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Reverse Linked List (pointer - Recursive)

easy

1. You are given a partially written LinkedList class. 2. You are required to complete the body of reversePR and reversePRHelper functions. The functions are expected to reverse the linked list by using recursion and changing the "next" data member of nodes. 3. Input and Output is managed for you. Note -> The online judge can't force you to write recursive function, nor can it check if you changed the "next" data member or not. But that is what the expectation is, the intention in to help you learn.

Constraints

1. Time complexity -> O(n) 2. Space complexity -> O(n)

Format

Input

Input is managed for you

Output

Output is managed for you

Example

Sample Input

11 1 2 3 4 5 6 7 8 9 10 11 100 200

Sample Output

1 2 3 4 5 6 7 8 9 10 11 200 11 10 9 8 7 6 5 4 3 2 1 100

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