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leetcode 19 Solution

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代码解析

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package com.demo.s19;

/**
 * 删除链表的倒数第 N 个结点
 * 给你一个链表，删除链表的倒数第 n 个结点，并且返回链表的头结点。
 */
class ListNode {
    int val;
    ListNode next;
    ListNode() {}
    ListNode(int val) { this.val = val; }
    ListNode(int val, ListNode next) { this.val = val; this.next = next; }
}
public class Solution {
    public ListNode removeNthFromEnd(ListNode head, int n) {
        ListNode dum = new ListNode(0, head);
        int cnt = 0;
        while(head != null) {
            cnt++;
            head = head.next;
        }

        head = dum;
        for(int i = 1; i< cnt-n + 1; i++) {
            head = head.next;
        }
        head.next = head.next.next;
        return dum.next;
    }
}