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Swap Nodes in Pairs
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 class Solution 2 { 3 public: 4 ListNode *swapPairs(ListNode *head) 5 { 6 if(head == NULL) return NULL; 7 ListNode *cur = head->next, *pre = head, *temp = NULL; 8 int i = 0; 9 while(cur)10 {11 if(i % 2 == 0)12 {13 pre->next = cur->next;14 cur->next = pre;15 if(i == 0)16 {17 head = cur;18 temp = head;19 }20 else21 {22 temp->next = cur;23 temp = temp->next;24 }25 cur = pre->next;26 }27 else28 {29 temp = temp->next;30 pre = pre->next;31 cur = cur->next;32 }33 i++;34 }35 return head;36 }37 };
Swap Nodes in Pairs
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