15 May | 1721. Swapping Nodes in a Linked List.cpp

/**
 * 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* swapNodes(ListNode* head, int k) {
        ListNode *ptr1 = head, *ptr2 = head, *kth = NULL;
        while(--k){
            ptr1 = ptr1->next;
        }

        kth = ptr1;
        ptr1 = ptr1->next;

        while(ptr1 != NULL){
            ptr1 = ptr1->next;
            ptr2 = ptr2->next;
        }

        swap(ptr2->val, kth->val);
        return head;
    }
};