Code360 powered by Coding Ninjas X Naukri.com. Code360 powered by Coding
Ninjas X Naukri.com

Problem of the day

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

```
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

```
1 <= T <= 5
0 <= L <= 10^5
1 <= data <= 10^9 and data != -1
Time Limit: 1 sec
```

```
1
1 2 3 4 5 6 -1
```

```
6 5 4 3 2 1 -1
```

```
For the first test case, After changing the next pointer of each node to the previous node, The given linked list is reversed.
```

```
1
10 21 3 2 4 -1
```

```
4 2 3 21 10 -1
```