删除链表中等于给定值 val 的所有节点。
示例:
输入: 1->2->6->3->4->5->6, val = 6
输出: 1->2->3->4->5
不使用虚拟头节点:
/**
* Definition for singly-linked list. public class ListNode { int val; ListNode
* next; ListNode(int x) { val = x; } }
*/
class Solution {
public ListNode removeElements(ListNode head, int val) {
while (head != null && head.val == val) {
ListNode delNode = head;
head = head.next;
delNode.next = null;
}
if (head == null) {
return null;
}
ListNode prev = head;
while (prev.next != null) {
if (prev.next.val == val) {
ListNode delNode = prev.next;
prev.next = delNode.next;
delNode.next = null;
} else {
prev = prev.next;
}
}
return head;
}
}
使用虚拟头节点:
/**
* Definition for singly-linked list. public class ListNode { int val; ListNode
* next; ListNode(int x) { val = x; } }
*/
class Solution {
public ListNode removeElements(ListNode head, int val) {
ListNode dummyHead = new ListNode(-1);// 传什么元素无所谓
dummyHead.next = head;
ListNode prev = dummyHead;
while (prev.next != null) {
if (prev.next.val == val) {
ListNode delNode = prev.next;
prev.next = delNode.next;
delNode.next = null;
} else {
prev = prev.next;
}
}
return dummyHead.next;
}
}
使用递归调用:
class Solution {
public ListNode removeElements(ListNode head, int val) {
if(head==null)
return null;
head.next=removeElements(head.next, val);
return head.val==val?head.next:head;
}
}