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[leetcode] problem 24 – swap nodes in pairs

admin 11月 13, 2020 0

Given a linked list, swap every two adjacent nodes and return its head.

You may not modify the values in the list, only nodes itself can be changed.

Example

Given 1->2->3->4, you should return the list as 2->1->4->3.

Code

public class  {
    int val;
    ListNode next;
    ListNode(int x) { val = x; }
}

public ListNode swapPairs(ListNode head) {
    ListNode node = new ListNode(0);
    node.next = head;
    ListNode prev = node;

    while (prev.next != null && prev.next.next != null) {
        ListNode current = prev.next;
        ListNode next = prev.next.next;
        current.next = next.next;
        next.next = current;
        prev.next = next;
        prev = current;
    }

    return node.next;
}