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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.
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 || head->next == NULL) return head;13 14 ListNode **prev = &head;15 while ((*prev) != NULL && ((*prev)->next) != NULL) {16 ListNode *pcurr = *prev;17 ListNode *pnext = (*prev)->next;18 pcurr->next = pnext->next;19 pnext->next = pcurr;20 *prev = pnext;21 prev = &(pcurr->next);22 }23 24 return head;25 }26 };
[LeetCode] Swap nodes in pairs
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