leetcode_swap_nodes_in_pairs

发表于

难度：Easy

解题思路：先在纸上画图。

dummy -> 1 -> 2 -> 3 -> 4

dummy    1 -> 2 -> 3 -> 4
  |           ^
  |___________|


         |---------|
         |         ^
dummy    1    2 -> 3 -> 4
  |           ^
  |___________|

         |---------|
         |         ^
dummy    1 <- 2    3 -> 4
  |           ^
  |___________|

代码如下：

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/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* swapPairs(ListNode* head) {
        ListNode* dummy = new ListNode(-1), *cur = dummy;
        dummy->next = head;
        while(cur->next != NULL && cur->next->next != NULL)
        {
            ListNode *first = cur->next;
            ListNode *second = first->next;
            cur->next = second;
            first->next = second->next;
            second->next = first;
            cur = first;
        }
        return dummy->next;
    }
};

运行结果：3ms，超过11.49％