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Swap Nodes in Pairs LeetCode Solution – Queslers

Problem – Swap Nodes in Pairs LeetCode Solution

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 = [1]
Output: [1]``````

Constraints:

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

Swap Nodes in Pairs LeetCode Solution in C++

``````ListNode* swapPairs(ListNode* head) {
if(!head || !head->next) return head; //If there are less than 2 nodes in the given nodes, then no need to do anything just return the list as it is.

ListNode* dummyNode = new ListNode();

ListNode* prevNode=dummyNode;

while(currNode && currNode->next){
prevNode->next = currNode->next;
currNode->next = prevNode->next->next;
prevNode->next->next = currNode;

prevNode = currNode;
currNode = currNode->next;
}

return dummyNode->next;
}

``````

Swap Nodes in Pairs LeetCode Solution in Java

``````public class Solution {
return n;
}
}
``````

Swap Nodes in Pairs LeetCode Solution in Python

``````class Solution(object):
dummy = ListNode(0)
cur = dummy

while cur.next and cur.next.next:
first = cur.next
sec = cur.next.next
cur.next = sec
first.next = sec.next
sec.next = first
cur = cur.next.next
return dummy.next
``````
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