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题解

代码

/** * Definition for singly-linked list. public class ListNode { int val; ListNode * next; ListNode(int x) { val = x; } } */

public class code19 {
    // public static ListNode removeNthFromEnd(ListNode head, int n) {
    // ListNode dummy = new ListNode(0);
    // dummy.next = head;
    // // 获取链表长度
    // int len = 0;
    // ListNode first = head;
    // while (first != null) {
    // len++;
    // first = first.next;
    // }
    // // 找到角标为(length - n - 1)的结点，让其next指向下下一个结点。
    // len = len - n;
    // first = dummy;
    // while (len > 0) {
    // len--;
    // first = first.next;
    // }
    // first.next = first.next.next;
    // return dummy.next;
    // }

    public static ListNode removeNthFromEnd(ListNode head, int n) {
        ListNode dummy = new ListNode(0);
        dummy.next = head;
        ListNode first = dummy;
        ListNode second = dummy;
        // 前进第一个指针，使第一个指针和第二个指针之间的间隙为n个节点
        for (int i = 1; i <= n + 1; i++) {
            first = first.next;
        }
        // 移动第一个指针到链表的末端，保持两个指针的间隙为n个节点
        while (first != null) {
            first = first.next;
            second = second.next;
        }
        second.next = second.next.next;
        return dummy.next;
    }

    public static void main(String[] args) {

        ListNode listNode1 = new ListNode(1);
        ListNode listNode2 = new ListNode(2);
        ListNode listNode3 = new ListNode(3);
        ListNode listNode4 = new ListNode(4);
        ListNode listNode5 = new ListNode(5);
        listNode1.next = listNode2;
        listNode2.next = listNode3;
        listNode3.next = listNode4;
        listNode4.next = listNode5;

        System.out.println(listNode1.val + " -> " + listNode2.val + " -> " + listNode3.val + " -> " + listNode4.val
                + " -> " + listNode5.val);

        int n1 = 2;

        ListNode result1 = removeNthFromEnd(listNode1, n1);

        System.out.println(result1.val + " -> " + result1.next.val + " -> " + result1.next.next.val + " -> "
                + result1.next.next.next.val);
    }
}
19. 删除链表的倒数第N个节点

题目

题解

代码

参考
