24. Swap Nodes in Pairs

Posted on | Edited on | In , |

题目

https://leetcode.com/problems/swap-nodes-in-pairs/description/

想法

比较简单，虽然没啥意思，但还是做一下

考虑头的变化，以及尾就没有问题了

答案

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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 *p = head;
        if (p == NULL || p->next == NULL)
            return p;
        p = head;
        ListNode *q = head->next->next;
        head = head->next;
        head->next = p;
        p->next = q;
        while(q != NULL && q->next != NULL) {
            p->next = q->next;
            ListNode *tmp = q->next->next;
            q->next = tmp;
            p = p->next->next;
            q = q->next;
        }
        return head;
    }
};