【Easy】451. Swap Nodes in Pairs

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

Example:

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

解题思路

错位设置指针的值，比如12反向，34反向，指针的值应该是01->23的顺序。

核心代码

    ListNode left = dummy, right = dummy.next;

    while (right != null && right.next != null) {
        left.next = right.next;
        right.next = left.next.next;
        left.next.next = right;
        left = right;
        right = right.next;
    }

时间空间复杂度

O(n) + S(1)