24. Swap Nodes in Pairs
Given a linked list, swap every two adjacent nodes and return its head.
For example,
Given 1->2->3->4, you should return the list as 2->1->4->3.
Your algorithm should use only constant space. You may not modify the values in the list, only nodes itself can be changed.
題目大意：
交換每兩個節點的位置。
代碼如下：
/**
* 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* left,*right,*pre,*p;
pre = NULL;//記錄每兩個節點前面的那個節點
p = head;
while(p !=NULL && p->next != NULL)
{
left = p;
right = p->next;
left->next = right->next;
right->next = left;
if(pre != NULL)
{
pre->next = right;
}
else//鏈表的頭兩個節點交換位置
{
head = right;
}
pre = left;
p = left->next;
}
return head;
}
};2016-08-12 23:51:00