6-9 删除单链表偶数节点 (14分)

本题要求实现两个函数，分别将读入的数据存储为单链表、将链表中偶数值的结点删除。链表结点定义如下：

struct ListNode {
    int data;
    struct ListNode *next;
};

函数接口定义：

struct ListNode *createlist();
struct ListNode *deleteeven( struct ListNode *head );

函数createlist从标准输入读入一系列正整数，按照读入顺序建立单链表。当读到−1时表示输入结束，函数应返回指向单链表头结点的指针。

函数deleteeven将单链表head中偶数值的结点删除，返回结果链表的头指针。

裁判测试程序样例：

#include <stdio.h>
#include <stdlib.h>

struct ListNode {
    int data;
    struct ListNode *next;
};

struct ListNode *createlist();
struct ListNode *deleteeven( struct ListNode *head );
void printlist( struct ListNode *head )
{
     struct ListNode *p = head;
     while (p) {
           printf("%d ", p->data);
           p = p->next;
     }
     printf("\n");
}

int main()
{
    struct ListNode *head;

    head = createlist();
    head = deleteeven(head);
    printlist(head);

    return 0;
}

/* 你的代码将被嵌在这里 */

struct ListNode *createlist(){
	struct ListNode *head=NULL,*now=NULL,*current;
	
	now=(struct ListNode *)malloc(sizeof(struct ListNode ));
	current=head=now;
	scanf("%d",&current->data);
	if(current->data==-1) return NULL;
	while(current->data!=-1){
		now=(struct ListNode *)malloc(sizeof(struct ListNode ));		
		scanf("%d",&now->data);	
		if(now->data==-1){
			current->next=NULL;
			break;
		}			
		else{
		current->next=now;		
		current=current->next;
		}		
	} 	
	return head;
}


struct ListNode *deleteeven( struct ListNode *head )//3
{
    struct ListNode * p=head,q;
    if(head==NULL)return NULL;
    while(head && head->data%2==0){ //保证头结点不是偶数        
        head = head->next;        //head->data%2==0&&head这样判断会出现段错误,好奇怪..	
    }//外层循环判断到结尾，内层循环连续删除
    p = head;
    while(p && p->next){
        while(p->next && p->next->data%2==0){
            p->next = p->next->next;
        }
        p = p->next;
    }
    return head;
}