Insert a dummy node before the head so that every pair has a consistent predecessor to rewire from.

Swap Nodes in Pairs

medium

Acceptance: 52%

Linked List

Given a linked list, swap every pair of adjacent nodes. For example, the first node swaps with the second, the third with the fourth, and so on. If the list has an odd number of nodes, the last node remains in place. You may not modify node values — only restructure the links.

Examples

Example 1:

Input:head = [5,10,15,20]

Output:[10,5,20,15]

Example 2:

Input:head = [3]

Output:[3]

Hints

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import java.util.*;

public class Main {
    public static void main(String[] args) {
        // Write your solution here
    }
}

import java.util.*;

public class Main {
    public static void main(String[] args) {
        // Write your solution here
    }
}

Swap Nodes in Pairs

Examples

Hints

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