[数据结构与算法]剑指offer java day11 双指针

T1 18. 删除链表的节点

class Solution {
    public ListNode deleteNode(ListNode head, int val) {
        ListNode node = head,per=null;
        if(head.val == val) //头节点的值就是目标值直接处理头
            head = head.next;
        else{
            while(node!=null){
                if(node.val == val){
                    per.next = node.next;
                }
                per = node; //记录前驱节点
                node = node.next;
            }
        }
        return head; 
    }
}

leetcode 评论区大佬还提供了一种思路用递归

T2 22. 链表中倒数第k个节点

由于倒数第k个节点说明最后输出的链表长度为k

设置双节点 latter ,former向后移动，当former为空时，latter就是结果

class Solution {
    public ListNode getKthFromEnd(ListNode head, int k) {
        ListNode former = head,latter=head;
        for(int i=0;i<k-1;i++){
            former = former.next; //former 先走k步
        }
        while(former.next!=null){
            former = former.next; 
            latter = latter.next;  
        }
        return latter;
        
    }
}