19-remove-nth-node-from-end-of-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) {}
 * };
 */

// ***********************************************************************************
// Problem link : https://leetcode.com/problems/remove-nth-node-from-end-of-list/

class Solution {
public:
    ListNode* removeNthFromEnd(ListNode* head, int n) {
        ListNode *dummy = new ListNode(0);
        dummy->next = head;
        ListNode *slow = dummy, *fast = dummy;
        while(n && fast->next)
        {
            fast = fast->next;
            n--;
        }
        while(fast->next)
        {
            slow = slow->next;
            fast = fast->next;
        }
        ListNode *temp = slow->next;
        slow->next = slow->next->next;
        delete temp;
        return dummy->next;
    }
};