LeetCode Algorithm 24. Exchange the nodes in the linked list in pairs

Topic link ：24. Two or two exchange nodes in a linked list

Ideas

Algorithm ： iteration
data structure ： Linked list
Ideas ： In fact, it is a bit similar to list flipping , It's just that every time you flip it, you flip it in pairs .

1. First create a virtual head node
2. As a virtual header node 、 The next node of the virtual head node 、 The next node of the virtual head node is defined as cur、first、second, Exchange two pointer operations
3. cur Keep going , Two steps at a time

Code

C++

class Solution {
    
public:
    ListNode* swapPairs(ListNode* head) {
    
		ListNode *dummyHead = new ListNode(0);
		dummyHead->next = head;
		ListNode *cur = dummyHead;
		while (cur->next != nullptr && cur->next->next != nullptr) {
    
			ListNode *first = cur->next, *second = cur->next->next;
			cur->next = second;
			first->next = second->next;
			second->next = first;
			cur = first;
		}
		return dummyHead->next;
    }
};