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