# Reverse a Linked List - Amazon Top Interview Questions

### Problem Statement :

Given a singly linked list node, return its reverse.

Bonus: Can you do this in \mathcal{O}(1)O(1) space?

Constraints

n ≤ 100,000 where n is the number of nodes in node

Example 1

Input

node = [1, 2, 3, 4]

Output

[4, 3, 2, 1]

Example 2

Input

node = [0, 1]

Output

[1, 0]

### Solution :

                        Solution in C++ :

/**
* class LLNode {
*     public:
*         int val;
*         LLNode *next;
* };
*/
LLNode* solve(LLNode* node) {
if (node == NULL) return node;
LLNode *curr, *nextt;
curr = node;
if (node->next == NULL)
return node;
else {
nextt = curr->next;

curr->next = NULL;
while (nextt) {
LLNode* temp = nextt->next;
nextt->next = curr;
curr = nextt;
nextt = temp;
}
}

return curr;
}


                        Solution in Python :

class Solution:
def solve(self, node):
return pre

"""
if not node or not node.next:
return node
node.next.next = node
node.next = None
"""


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