leetcode笔记：Remove Linked List Elements

一. 题目描述

Remove all elements from a linked list of integers that have value val.

Example Given: 1 --> 2 --> 6 --> 3 --> 4 --> 5 --> 6, val = 6 Return: 1 --> 2 --> 3 --> 4 --> 5

Credits: Special thanks to @mithmatt for adding this problem and creating all test cases.

二. 题目分析

题目大意是从单链表中移除所有值为val的元素。在循环遍历链表时使用cur记录当前元素。注意多种临界情况，如头结点为NULL的时候。

三. 示例代码

// C++版本ListNode* removeElements(ListNode* head, int val) {    ListNode* cur = head;    while (true) {        if (head == NULL) return NULL;        if (cur->val != val) break;        cur = cur->next;        head = cur;    }    while (cur->next) {        if (cur->next->val == val) {            cur->next = cur->next->next;        } else {            cur = cur->next;        }    }    return head;}

// Python版本# Definition for singly-linked list.# class ListNode:#    def __init__(self, x):#        self.val = x#        self.next = Noneclass Solution:    # @param {ListNode} head    # @param {integer} val    # @return {ListNode}    def removeElements(self, head, val):        pre = ListNode(0)        pre.next = head        cur = pre        while cur and cur.next:            if cur.next.val == val:                cur.next = cur.next.next            else:                cur = cur.next        return pre.next

四. 小结

以上代码可以AC，但在编写过程中并没有考虑delete节点的问题，这样是不对的，由于时间有限，只能下次再改进了。