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Leetcode | 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.
比起第一次写简洁多了。
1 /** 2 * Definition for singly-linked list. 3 * struct ListNode { 4 * int val; 5 * ListNode *next; 6 * ListNode(int x) : val(x), next(NULL) {} 7 * }; 8 */ 9 class Solution {10 public:11 ListNode *swapPairs(ListNode *head) {12 if (head == NULL) return head;13 ListNode h(0), *first = head, *second, *prev = &h, *nextFirst;14 h.next = head;15 16 while (first) {17 second = first->next;18 if (!second) break;19 prev->next = second;20 nextFirst = second->next;21 second->next = first;22 first->next = nextFirst;23 prev = first;24 first = nextFirst;25 }26 27 return h.next;28 }29 };
Leetcode | Swap Nodes in Pairs
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