week10-leetcode #24-Swap-Nodes-in-Pairs

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

Question

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.

Solution

time complecity: O(n)

space complecity:O(n)

class Solution {  public:    ListNode* swapPairs(ListNode* head) {      int pre_val = 0;      int post_val = 0;      ListNode* p = head;      // 不断往前交换数据      while (p != NULL && p->next != NULL) {        pre_val = p->val;        post_val = p->next->val;        p->val = post_val;        p->next->val = pre_val;        p = p->next->next;      }      return head;    }};

思路：本题目只对偶数对进行处理，也就是（0，1）、（2，3）、（4，5）等进行配对（下标从0开始），最后的奇数即可以直接忽略不处理。