In this post, we are going 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.
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 = [1] Output: [1]
Constraints:
- The number of nodes in the list is in the range
[0, 100]. 0 <= Node.val <= 100
Now, let’s see the leetcode solution of Swap Nodes in Pairs Leetcode Solution.
Swap Nodes in Pairs Leetcode Solution in Python
class Solution:
def swapPairs(self, head: ListNode) -> ListNode:
def getLength(head: ListNode) -> int:
length = 0
while head:
length += 1
head = head.next
return length
length = getLength(head)
dummy = ListNode(0, head)
prev = dummy
curr = head
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 Solution in CPP
class Solution {
public:
ListNode* swapPairs(ListNode* head) {
const int length = getLength(head);
ListNode dummy(0, head);
ListNode* prev = &dummy;
ListNode* curr = head;
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 getLength(ListNode* head) {
int length = 0;
for (ListNode* curr = head; curr; curr = curr->next)
++length;
return length;
}
};
Swap Nodes in Pairs Leetcode Solution in Java
class Solution {
public ListNode swapPairs(ListNode head) {
final int length = getLength(head);
ListNode dummy = new ListNode(0, head);
ListNode prev = dummy;
ListNode curr = head;
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;
}
private int getLength(ListNode head) {
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 Chase2learn This tutorial is only for Educational and Learning purposes.
