3. Reverse a LL

Given the head of a singly linked list. Reverse the given linked list and return the head of the modified list.

Example 1:

Input: head = [1, 2, 3, 4, 5]

Output: [5, 4, 3, 2, 1]

Explanation: The linked list is reversed by changing the direction of each link between consecutive nodes, resulting in the list [5, 4, 3, 2, 1].

Example 2:

Input: head = [6, 8]

Output: [8, 6]

Explanation: The link between the two nodes is reversed, changing the list from 6->8 to 8->6.

Now Your Turn!

Pick the correct output for the given input

Input: head = [1]

Still unsure what the problem is asking ?

Let’s go through a few more examples, step by step, to make it clearer.

Constraints:

  • 0 <= number of nodes in the Linked List <= 105
  • 0 <= ListNode.val <= 104

Hints

Frequently Occurring Doubts

Interview Follow-up Questions

0
/*
Definition of singly linked list:
struct ListNode
{
int val;
ListNode *next;
ListNode()
{
val = 0;
next = NULL;
}
ListNode(int data1)
{
val = data1;
next = NULL;
}
ListNode(int data1, ListNode *next1)
{
val = data1;
next = next1;
}
};
*/
 
class Solution {
public:
ListNode* reverseList(ListNode* head) {
}
};
Test Case

Input:

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