Print reverse of a Linked List without actually reversing
Given a linked list, print reverse of it using a recursive function. For example, if the given linked list is 1->2->3->4, then output should be 4->3->2->1.
Note that the question is only about printing the reverse. To reverse the list itself see this
Difficulty Level: Rookie
Algorithm
printReverse(head) 1. call print reverse for head->next 2. print head->data
Implementation:
C++
// C++ program to print reverse of a linked list #include <bits/stdc++.h> using namespace std; /* Link list node */class Node { public: int data; Node* next; }; /* Function to reverse the linked list */void printReverse(Node* head) { // Base case if (head == NULL) return; // print the list after head node printReverse(head->next); // After everything else is printed, print head cout << head->data << " "; } /*UTILITY FUNCTIONS*//* Push a node to linked list. Note that this function changes the head */void push(Node** head_ref, char new_data) { /* allocate node */ Node* new_node = new Node(); /* put in the data */ new_node->data = new_data; /* link the old list off the new node */ new_node->next = (*head_ref); /* move the head to pochar to the new node */ (*head_ref) = new_node; } /* Driver code*/int main() { // Let us create linked list 1->2->3->4 Node* head = NULL; push(&head, 4); push(&head, 3); push(&head, 2); push(&head, 1); printReverse(head); return 0; } // This code is contributed by rathbhupendra |
C
// C program to print reverse of a linked list #include<stdio.h> #include<stdlib.h> /* Link list node */struct Node { int data; struct Node* next; }; /* Function to reverse the linked list */void printReverse(struct Node* head) { // Base case if (head == NULL) return; // print the list after head node printReverse(head->next); // After everything else is printed, print head printf("%d ", head->data); } /*UTILITY FUNCTIONS*//* Push a node to linked list. Note that this function changes the head */void push(struct Node** head_ref, char new_data) { /* allocate node */ struct Node* new_node = (struct Node*) malloc(sizeof(struct Node)); /* put in the data */ new_node->data = new_data; /* link the old list off the new node */ new_node->next = (*head_ref); /* move the head to pochar to the new node */ (*head_ref) = new_node; } /* Driver program to test above function*/int main() { // Let us create linked list 1->2->3->4 struct Node* head = NULL; push(&head, 4); push(&head, 3); push(&head, 2); push(&head, 1); printReverse(head); return 0; } |
Java
// Java program to print reverse of a linked list class LinkedList { Node head; // head of list /* Linked list Node*/ class Node { int data; Node next; Node(int d) {data = d; next = null; } } /* Function to print reverse of linked list */ void printReverse(Node head) { if (head == null) return; // print list of head node printReverse(head.next); // After everything else is printed System.out.print(head.data+" "); } /* Utility Functions */ /* Inserts a new Node at front of the list. */ public void push(int new_data) { /* 1 & 2: Allocate the Node & Put in the data*/ Node new_node = new Node(new_data); /* 3. Make next of new Node as head */ new_node.next = head; /* 4. Move the head to point to new Node */ head = new_node; } /*Driver function to test the above methods*/ public static void main(String args[]) { // Let us create linked list 1->2->3->4 LinkedList llist = new LinkedList(); llist.push(4); llist.push(3); llist.push(2); llist.push(1); llist.printReverse(llist.head); } } /* This code is contributed by Rajat Mishra */ |
Python3
# Python3 program to print reverse # of a linked list # Node class class Node: # Constructor to initialize # the node object def __init__(self, data): self.data = data self.next = None class LinkedList: # Function to initialize head def __init__(self): self.head = None # Recursive function to print # linked list in reverse order def printrev(self, temp): if temp: self.printrev(temp.next) print(temp.data, end = ' ') else: return # Function to insert a new node # at the beginning def push(self, new_data): new_node = Node(new_data) new_node.next = self.head self.head = new_node # Driver code llist = LinkedList() llist.push(4) llist.push(3) llist.push(2) llist.push(1) llist.printrev(llist.head) # This code is contributed by Vinay Kumar(vinaykumar71) |
C#
// C# program to print reverse of a linked list using System; public class LinkedList { Node head; // head of list /* Linked list Node*/ class Node { public int data; public Node next; public Node(int d) { data = d; next = null; } } /* Function to print reverse of linked list */ void printReverse(Node head) { if (head == null) return; // print list of head node printReverse(head.next); // After everything else is printed Console.Write(head.data + " "); } /* Utility Functions */ /* Inserts a new Node at front of the list. */ public void push(int new_data) { /* 1 & 2: Allocate the Node & Put in the data*/ Node new_node = new Node(new_data); /* 3. Make next of new Node as head */ new_node.next = head; /* 4. Move the head to point to new Node */ head = new_node; } /*Driver function to test the above methods*/ public static void Main(String []args) { // Let us create linked list 1->2->3->4 LinkedList llist = new LinkedList(); llist.push(4); llist.push(3); llist.push(2); llist.push(1); llist.printReverse(llist.head); } } // This code has been contributed by Rajput-Ji |
Output:
4 3 2 1
Time Complexity: O(n)
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