[C语言][LeetCode][203]Remove Linked List Elements

题目

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

标签

Linked List

难度

简单

分析

题目意思是给定一个单链表和一个value，删除链表里和value相同的节点，返回新的链表。我的做法是先找到要返回链表的头结点，然后遍历链表，如果遇到和value不相同的节点，则保存节点，否则跳过。

C代码实现

struct ListNode* removeElements(struct ListNode* head, int val) 
{
    struct ListNode * p;
    struct ListNode * q;
    struct ListNode * ret;

    if(!head)
        return NULL;

    p = head;

    while(p && (p->val == val))     // find the head of the return list
    {
        p = p->next;
    }

    if(!p)
        return NULL;

    q = p;
    ret = q;                                   // keep the first element of the return list

    p = p->next;

    while(p)
    {
        if(p->val != val)                 // if val is not equal the p->val, save it to the return list
        {
            q->next = p;
            q = p;
        }

        p = p->next;
    }

    q->next =NULL;

    return ret;
}