# Swap Nodes in Pairs Leetcode Solution In this post, you will know how to solve the Swap Nodes in Pairs Leetcode Solution problem of Leetcode. This Leetcode problem is done in many programming languages like C++, Java, and Python.

One more thing to add, don’t directly look for the solutions, first try to solve the problems of Leetcode by yourself. If you find any difficulty after trying several times, then you can look for solutions.

## Problem

Given a linked list, swap every two adjacent nodes and return its head. You must solve the problem without modifying the values in the list’s nodes (i.e., only nodes themselves may be changed.)

Example 1:

```Input: head = [1,2,3,4]
Output: [2,1,4,3]
```

Example 2:

```Input: head = []
Output: []
```

Example 3:

```Input: head = 
Output: 
```

Constraints:

• The number of nodes in the list is in the range `[0, 100]`.
• `0 <= Node.val <= 100`

### Swap Nodes in Pairs Leetcode Solutions in Python

```class Solution:
def swapPairs(self, head: ListNode) -> ListNode:
length = 0
length += 1
return length
prev = dummy
for _ in range(length // 2):
next = curr.next
curr.next = next.next
next.next = prev.next
prev.next = next
prev = curr
curr = curr.next
return dummy.next
```

### Swap Nodes in Pairs Leetcode Solutions in CPP

```class Solution {
public:
ListNode* prev = &dummy;
for (int i = 0; i < length / 2; ++i) {
ListNode* next = curr->next;
curr->next = next->next;
next->next = prev->next;
prev->next = next;
prev = curr;
curr = curr->next;
}
return dummy.next;
}
private:
int length = 0;
for (ListNode* curr = head; curr; curr = curr->next)
++length;
return length;
}
};
```

### Swap Nodes in Pairs Leetcode Solutions in Java

```class Solution {
ListNode dummy = new ListNode(0, head);
ListNode prev = dummy;
for (int i = 0; i < length / 2; ++i) {
ListNode next = curr.next;
curr.next = next.next;
next.next = curr;
prev.next = next;
prev = curr;
curr = curr.next;
}
return dummy.next;
}
int length = 0;
for (ListNode curr = head; curr != null; curr = curr.next)
++length;
return length;
}
}
```

Note: This problem Swap Nodes in Pairs is generated by Leetcode but the solution is provided by BrokenProgrammers. This tutorial is only for Educational and Learning purposes.