【算法刷题day3】Leetcode: 203.移除链表元素、707.设计链表、 206.反转链表-Leetcode 203.移除链表元素

题目：203.移除链表元素
解析：2.5 练习时长两年半

解题思路

使用虚拟头节点，判定下一个节点是否为val，若为val，则删除下一个节点

代码

/**
 * 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(-1, head);
        ListNode cur = dummy;
        while (cur.next != null){
            if (cur.next.val == val){
                cur.next = cur.next.next;
            }else{
                cur = cur.next;
            }
        }
        return dummy.next;

    }
}

总结

没试过不适用虚拟头节点

/**
 * 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) {
        while (head != null && head.val == val){
            head = head.next;
        }
        if (head == null)
            return head;
        ListNode cur = head;
        while (cur.next != null){
            if (cur.next.val == val)
                cur.next = cur.next.next;
            else
                cur = cur.next;
        }
        return head;

    }
}