C语言猜拳游戏循环问题求助：输入y重启游戏失败

问题出在C语言的输入缓冲区残留换行符上：scanf读取字符时不会自动跳过输入后的换行，这些残留的换行会被下一次scanf直接读取，导致程序跳过你的输入提示。

给你两种可行的修复方案：

方案一：在%c前添加空格 #

scanf的格式控制符里，%c前的空格会让它自动跳过所有空白字符（包括换行、空格、制表符），直接读取有效输入字符，完美避开残留换行的问题。修改所有读取字符的scanf语句即可：

#include<stdio.h>

int main (){
char firstPlayer, secondPlayer, again;
do{
printf("Jack 'n Poy\nEnter Player 1 input: ");
scanf(" %c", &firstPlayer); // %c前添加空格

printf("Enter Player 2 input: ");
scanf(" %c", &secondPlayer); // 同样添加空格

switch (firstPlayer){
    case 'x':
    switch (secondPlayer){
        case 'x':
        printf("Draw");
        break; 
        case 's':
        printf("Player 2 wins");
        break;
        case 'p':
        printf("Player 1 wins");
        
    }
    break;
     case 's':
     switch (secondPlayer){
        case 'x':
        printf("Player 1 wins");
        break;
        case 's':
        printf("Draw");
        break;
        case 'p':
        printf("Player 2 wins");
    }
    break;
     case 'p':
     switch (secondPlayer){
        case 'x':
        printf("Player 2 wins");
        break;
        case 's':
        printf("Player 1 wins");
        break;
        case 'p':
        printf("Draw");
     }
    break;
    default:
    printf("Invalid input");
    
}
    printf("\nPlay again? (y/n)");
    scanf(" %c", &again); // 此处也添加空格
}
while (again == 'y');
printf("Thank you for playing");

return 0;
}

方案二：手动清理输入缓冲区 #

每次用scanf读取字符后，调用循环把缓冲区里的残留字符（直到换行）全部清空，彻底避免残留字符影响下一次输入：

#include<stdio.h>

int main (){
char firstPlayer, secondPlayer, again;
do{
printf("Jack 'n Poy\nEnter Player 1 input: ");
scanf("%c", &firstPlayer);
while(getchar() != '\n'); // 清理缓冲区到换行符为止

printf("Enter Player 2 input: ");
scanf("%c", &secondPlayer);
while(getchar() != '\n'); // 同样清理缓冲区

switch (firstPlayer){
    case 'x':
    switch (secondPlayer){
        case 'x':
        printf("Draw");
        break; 
        case 's':
        printf("Player 2 wins");
        break;
        case 'p':
        printf("Player 1 wins");
        
    }
    break;
     case 's':
     switch (secondPlayer){
        case 'x':
        printf("Player 1 wins");
        break;
        case 's':
        printf("Draw");
        break;
        case 'p':
        printf("Player 2 wins");
    }
    break;
     case 'p':
     switch (secondPlayer){
        case 'x':
        printf("Player 2 wins");
        break;
        case 's':
        printf("Player 1 wins");
        break;
        case 'p':
        printf("Draw");
     }
    break;
    default:
    printf("Invalid input");
    
}
    printf("\nPlay again? (y/n)");
    scanf("%c", &again);
    while(getchar() != '\n'); // 清理最后一次输入的缓冲区
}
while (again == 'y');
printf("Thank you for playing");

return 0;
}

额外说明 #

你原代码中第一个scanf("%c ", &firstPlayer);后面的空格会导致scanf等待非空白字符，反而会加重输入混乱，所以直接去掉该空格，改用上面两种方案之一即可。

内容的提问来源于stack exchange，提问作者Mr. Skadoosh