remove-nth-node-from-end-of-list.cpp

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* removeNthFromEnd(ListNode* head, int n) {
        
        ListNode* HEAD = new ListNode(-1);
        HEAD->next = head;
        
        ListNode* fast = nullptr;
        ListNode* slow = nullptr;
        
        fast = HEAD;
        
        int step = n + 1;
        while(step--){
            fast = fast->next;
        }
        

        
        slow = HEAD;
        
        while(fast){
            slow = slow->next;
            fast = fast->next;
        }

        
        slow->next = slow->next->next;
        
        return HEAD->next;
        
    }
};