24. Swap Nodes in Pairs

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    ListNode* swap(ListNode* first,ListNode* second){
        first->next=second->next;
        second->next=first;
        return second;
    }
    ListNode* swapPairs(ListNode* head) {
        ListNode *temp=new ListNode();
        temp->next=head;
        ListNode*curr=temp;
        
        while(curr!=NULL && curr->next!=NULL &&curr->next->next!=NULL){
            curr->next=swap(curr->next,curr->next->next);
            curr=curr->next->next;
        }
        return temp->next;
    }
};