leetcode 203 移除链表元素

//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
// 
// Related Topics 链表 
// 👍 531 👎 0


//leetcode submit region begin(Prohibit modification and deletion)
/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode removeElements(ListNode head, int val) {
        ListNode dummy = new ListNode(0);
        dummy.next = head;
        ListNode prev = dummy;
        while(head != null){
            if(head.val == val){
                prev.next = head.next;
            }else{
                prev = head;
            }
            head = head.next;
        }
        return dummy.next;
    }
}
//leetcode submit region end(Prohibit modification and deletion)

主要理解点：prev和head的移动

初始prev=dummy

dummy.next = head

当 head.val条件不满足时指定prev位置prev=head,然后再把head 移到下一个元素head = head.next.