[LeetCode] Remove Linked List Elements

Remove Linked List Elements

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.

解题思路：

这道题挺简单的，注意队首为val值的情况即可。

/**
 * 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) {
        ListNode* p=NULL, *q=NULL;
        while(head!=NULL&&head->val==val){  //对于队首的情况
            p=head;
            head=head->next;
            delete p;
        }
        p=head;
        while(p!=NULL&&p->next!=NULL){
            if(p->next->val==val){
                q=p->next;
                p->next=q->next;
                delete q;
            }else{
                p=p->next;
            }
        }
        return head;
    }
};

为简化代码，建立一个伪头结点，其next指向head，这样所有的操作都是一样，能够简化代码。

/**
 * 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) {
        ListNode* myHead=new ListNode(0);
        myHead->next=head;
        ListNode* p=myHead, *q=NULL;
        while(p->next!=NULL){
            if(p->next->val==val){
                q=p->next;
                p->next=q->next;
                delete q;
            }else{
                p=p->next;
            }
        }
        head=myHead->next;
        delete myHead;
        return head;
    }
};

[LeetCode] Remove Linked List Elements

原文：http://blog.csdn.net/kangrydotnet/article/details/45220391