Reverse a Linked List

Problem

Given a linked list, reverse the nodes of the list and return the new head node.
Example input:
1 -> 2 -> 3 -> 4 -> 5
Example output:
5 -> 4 -> 3 -> 2 -> 1

Solution

This solution is in C++. Our A.I. can create solutions in multiple languages.

kayakane

#include <iostream>

using namespace std;

struct Node {
    int data;
    Node *next;
};

Node *reverse(Node *head) {
    Node *prev = NULL;
    Node *curr = head;
    Node *next = NULL;

    while (curr != NULL) {
        next = curr->next;
        curr->next = prev;
        prev = curr;
        curr = next;
    }

    return prev;
}

void printList(Node *head) {
    Node *curr = head;
    while (curr != NULL) {
        cout << curr->data << " ";
        curr = curr->next;
    }
    cout << endl;
}

int main() {
    Node *head = new Node;
    head->data = 1;
    head->next = new Node;
    head->next->data = 2;
    head->next->next = new Node;
    head->next->next->data = 3;
    head->next ->next->next = new Node;
    head->next->next->next->data = 4;
    head->next->next->next->next = new Node;
    head->next->next->next->next->data = 5;
    head->next->next->next->next->next = NULL;

    printList(head);
    head = reverse(head);
    printList(head);

    return 0;
}