如何删除链表倒数第K个元素

数据结构与算法

快慢指针，有点变化的是这个k是从0还是从1开始，这样的变化在快指针进行计数的时候有变化。
结束的还是根据快指针的next来判断。

1.首发

class ListNode {
    int val;
    ListNode next;
    public ListNode(int val) {
        this.val = val;
    }
}
public class Solution {
    //k为倒数
    public ListNode remove(ListNode list, int k) {
        ListNode head = list;
        ListNode fast = head;
        ListNode slow = head;
        int counter = 0;
        while (fast != null) {
            if (counter == k + 1) {//这里
                break;
            }
            counter++;
            fast = fast.next;
        }
        while (slow != null) {
            if (fast.next == null) {
                slow.next = slow.next.next;
                break;
            }
            fast = fast.next;
            slow = slow.next;
        }
        return head;
    }
    public void print(ListNode head) {
        while (head != null) {
            System.out.print(" " + head.val);
            head = head.next;
        }
    }
    public ListNode getListNode() {
        ListNode head = null;
        ListNode p = null;
        for (int i = 0; i < 10; i++) {
            ListNode node = new ListNode(i);
            if (head == null) {
                head = node;
                p = head;
            } else {
                p.next = node;
                p = p.next;
            }
        }
        return head;
    }
    public static void main(String[] args) {
        ListNode head;
        Solution solution = new Solution();
        head = solution.getListNode();
        solution.print(head);
        solution.remove(head, 2);
        System.out.println();
        solution.print(head);
    }
}

2.重构

 public ListNode remove(ListNode list, int k) {
        ListNode head = list;
        ListNode fast = head;
        ListNode slow = head;
        for (int i = 0; i < k+1; i++) {
            fast = fast.next;
        }
        while (fast.next != null) {
            fast = fast.next;
            slow = slow.next;
        }
        slow.next = slow.next.next;
        return slow;
    }

总结，这个移动指定数值个点还是用能控制次数的循环比较快。