**Pairwise Linked List Swap - Amazon Top Interview Questions**

### Problem Statement :

Given a singly linked list node, swap each pair of nodes and return the new head. Constraints n ≤ 100,000 where n is the number of nodes in node Example 1 Input node = [0, 1, 3, 4] Output [1, 0, 4, 3] Example 2 Input node = [1, 2, 3] Output [2, 1, 3]

### Solution :

` ````
Solution in C++ :
/**
* class LLNode {
* public:
* int val;
* LLNode *next;
* };
*/
LLNode* solve(LLNode* node) {
if (!node) return node;
// LLNode* hd=node;
LLNode* tmp = node;
if (node && node->next) {
tmp = node->next;
node->next = node->next->next;
tmp->next = node;
node->next = solve(tmp->next->next);
}
return tmp;
}
```

` ````
Solution in Python :
# class LLNode:
# def __init__(self, val, next=None):
# self.val = val
# self.next = next
class Solution:
def solve(self, node):
if not node or not node.next:
return node
tail = self.solve(node.next.next)
head = node.next
head.next = node
node.next = tail
return head
```

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