C/我如何从这里到达第 2 阶段？它只是循环并直接进入第 3 阶段

Question

这是贪吃蛇游戏的部分代码。我想做的是制作关卡(大约3个)，如果分数达到一定的分数(100或200)，关卡就会改变。

在这段代码中，我尝试让分数达到 100 时进入第 2 阶段。但正如我编码的那样，它只是在 main 函数中循环并直接进入 stage3。

这是主要代码:

int main(){

title(); 

while(1)
{
    if(kbhit()) do{key=getch();} while(key==224); // Key input
    Sleep(speed);

    switch(key) // Apprehend the key and runs the program
    {  
        case LEFT:
        case RIGHT:
        case UP:
        case DOWN:
            if( (dir==LEFT&&key!=RIGHT)||(dir==RIGHT&&key!=LEFT)||(dir==UP&&key!=DOWN)||
                (dir==DOWN&&key!=UP)) // Need for prevent the 180 degrees rotational movement
                dir=key;
            key=0; // Reset the key to 0
        break;

        case PAUSE: 
            pause();
        break;

        case 115: // input 'S', then status() activated
            if(status_on==0) status_on=1;
            else status_on=0;
            key=0;
            break;

        case ESC: // Program exits if the input value is ESC
            exit(0);
    }
    move(dir); 
    if(status_on==1) status();
}    

如您所见，移动函数位于 while(1) 中。

这是 move(dir) 的代码:

void move(int dir)
{
int i, j;

if(x[0]==food_x&&y[0]==food_y) // Case when it hits with food
{  
    score+=10;  
    food();  
    length++;  
    x[length-1]=x[length-2];  
    y[length-1]=y[length-2];
}
for (j = 0; j < num_of_bombs; j++)
{
    if (x[0] == bomb_x[j] && y[0] == bomb_y[j]) // Case when it hits with bomb
    {
        score -= 10;

        for (j = 0; j < num_of_bombs; j++)
            gotoxy(MAP_ADJ_X + bomb_x[j], MAP_ADJ_Y + bomb_y[j], " "); // Delets the lastest bombs

        bomb();
        gotoxy(MAP_ADJ_X + x[length - 1], MAP_ADJ_Y + y[length - 1], " "); // Delets the last body of the snake
        length--;
    }
}
if(x[0]==0||x[0]==MAP_X-1||y[0]==0||y[0]==MAP_Y-1) // Case when it hits the wall
{  
    game_over();
    return;  
}
for(i=1;i<length;i++) // Case when it hits itself
{  
    if(x[0]==x[i]&&y[0]==y[i])
    {
        game_over();
        return;
    }
}

gotoxy(MAP_ADJ_X+x[length-1],MAP_ADJ_Y+y[length-1],"  "); // Delets it's last one
for(i=length-1;i>0;i--) // Move the coordinates one by one
{  
    x[i]=x[i-1];
    y[i]=y[i-1];
}
gotoxy(MAP_ADJ_X+x[0],MAP_ADJ_Y+y[0],"▣"); // Part that changes head to body. But in this code, it is unnecessery
if(dir==LEFT) --x[0];  
if(dir==RIGHT) ++x[0];
if(dir==UP) --y[0]; 
if(dir==DOWN) ++y[0];     
gotoxy(MAP_ADJ_X+x[i],MAP_ADJ_Y+y[i],"▣"); // Part that puts new head. But unnecessery in this code

if (length < 2) // If length goes down below 2, gmae is over
    game_over();

switch (score)
{
case 100:
case 200:
    ++stage;
    break;
}

switch (stage)
{
case 2:
    stage2();
case 3:
    stage3();
}
}

有人可以帮我吗？

最好，

兰迪

Answer 1

默认情况下，switch 语句中的情况会失败，除非包含 break。在你的代码中你有

switch(stage) 
{
case 2:
    stage2();
    // Here there is an implicit fall through because a break statement is missing.
case 3:
    // This gets executed if stage == 3 but also if stage == 2
    // because of the fall through you first go to stage2() and then immediately afterwards to stage3()
    stage3();
}

解决方案是在调用 stage2() 之后添加 break;。

此行为会导致许多问题，以至于 gcc 等编译器具有选项 -Wimplicit-fallthrough。使用该选项，每次您有意使用该行为时，都必须添加类似 //fall-through 的注释。