#include <stdio.h>
#include <malloc.h>
#include <stdlib.h>
#include <time.h>
#include <conio.h>
#include <string.h>



#define N 20

int SPEED;

int game[N][N];

enum
{
    UP,DOWN,LEFT,RIGHT
}point;

typedef struct snake
{
    struct snake* perior;
    struct snake* next;
        int x;
        int y;
}snake;
snake *head,*tail;

struct Foodinfo
{
    int food_x;
    int food_y;
}food;

void greate_food()
{
    srand((unsigned)time(NULL));
    do
    {
    food.food_x=rand()%18;
    food.food_y=rand()%18;
    }while(1==game[food.food_x][food.food_y]);
    game[food.food_x][food.food_y]=1;
}
void add_head(int a,int b)
{
    snake *temp=(struct snake*)malloc(sizeof(struct snake));
    temp->x=a;
    temp->y=b;
    temp->perior =NULL;
    if(head==NULL)
    {
        head=tail=temp;
        temp->perior=NULL;
    }
    else
    {
        head->perior = temp;
        temp->next = head;
        head=head->perior;
    }
    game[a][b]=1;
}

void delete_tail()
{
    snake *temp=tail;
    game[tail->x][tail->y]=0;
    tail=temp->perior;
    tail->next=NULL;
    free(temp);
}

void move()
{
    void output();
    void greate_food();   
    int    a=head->x;
    int    b=head->y;
   
    switch(point)
    {
        case UP:--a;break;
        case DOWN:++a;break;
        case LEFT:--b;break;
        case RIGHT:++b;break;
    }

    if(1==game[a][b]&& a !=food.food_x && b!=food.food_y)
    {
        output();
        printf("YOU ARE LOSE !\n");
        exit(0);
    }
    if(a==food.food_x && b==food.food_y)
    {
        add_head(a,b);
        greate_food();
        return ;
    }

    add_head(a,b);
    delete_tail();

}

void change_point(char keydown)
{
   
    switch(keydown)
    {
        case 'w':
        case 'W':point=UP;break;
        case 's':
        case 'S':point=DOWN;break;
        case 'a':
        case 'A':point=LEFT;break;
        case 'd':
        case 'D':point=RIGHT;break;
    }
}

void init()
{
    int i;
    for(i=0;i<=N-1;i++)
    {
        game[i][0]=game[i][N-1]=1;
        game[0][i]=game[N-1][i]=1;
    }
    head=tail;
    point=RIGHT;
    add_head(6,4);
    add_head(6,5);
    add_head(6,6);
}

void output()
{
    int i,j;
    for(i=0;i<=    N-1;i++)
    {
        for(j=0;j<=N-1;j++)
        {
            if(1==game[i][j])
                printf("* ");
            else
                printf("  ");
        }
            printf("\n");
    }
}



int main()
{
    char level;
c1:    printf("请选择游戏难度：\n 简单： 1 / 普通： 2 / 困难： 3\n");
        level=getch();
    switch(level)
    {
    case '1':SPEED=500;break;
    case '2':SPEED=200;break;
    case '3':SPEED=50;break;
    default :
        {
            system("cls");
            printf("请输入正确的选项。\n");
            goto c1;
        }
    }
    init();
    greate_food();
    output();
    printf("操作方法：W ↑S ↓A ←D →\n按任意键开始游戏");
    while(1)
    {
        char keydown=getch();
        change_point(keydown);
        while(!kbhit())
        {   
                system("cls");
            move();
            output();
            _sleep(SPEED);
        }
    }
}