LeetCode（203） Remove LinkedList Elements

题目

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.

分析

删除链表中的指定值的节点。

需要注意的是，所需要删除节点的位置，头，中间，尾，不同位置需要不同处理，避免断链~

AC代码

/** * Definition for singly-linked list. * struct ListNode { *     int val; *     ListNode *next; *     ListNode(int x) : val(x), next(NULL) {} * }; */class Solution {public:    ListNode* removeElements(ListNode* head, int val) {        if (head == NULL)            return head;        ListNode *pre = head, *p = head;        while (p)        {            //找到要删除的节点元素            if (p->val == val)            {                //判断当前节点为头结点                if (p == head)                {                    head = p->next;                    ListNode *q = p;                    //更新头                    p = head;                    pre = head;                    delete q;                    q = NULL;                }                //删除尾节点                else if (p->next == NULL)                {                    pre->next = NULL;                                   delete p;                    p = NULL;                }                //删除链表中间节点                else{                    pre->next = p->next;                    ListNode *q = p;                    p = p->next;                    delete q;                    q = NULL;                }//else            }//if            else{                pre = p;                p = p->next;            }        }//while        return head;    }};

GitHub测试程序源码