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# Reverse Linked List

Moderate
0/80
Average time to solve is 15m
Contributed by

## Problem statement

Given a singly linked list of integers. Your task is to return the head of the reversed linked list.

For example:
``````The given linked list is 1 -> 2 -> 3 -> 4-> NULL. Then the reverse linked list is 4 -> 3 -> 2 -> 1 -> NULL and the head of the reversed linked list will be 4.
``````
``````Can you solve this problem in O(N) time and O(1) space complexity?
``````
Detailed explanation ( Input/output format, Notes, Images )
Constraints :
``````1 <= T <= 5
0 <= L <= 10^5
1 <= data <= 10^9 and data != -1

Time Limit: 1 sec
``````
##### Sample Input 1 :
``````1
1 2 3 4 5 6 -1
``````
##### Sample Output 1 :
``````6 5 4 3 2 1 -1
``````
##### Explanation For Sample Input 1 :
``````For the first test case,  After changing the next pointer of each node to the previous node, The given linked list is reversed.
``````
##### Sample Input 2 :
``````1
10 21 3 2 4 -1
``````
##### Sample Output 2 :
``````4 2 3 21 10 -1
``````
Console