include <stdio.h>

int main(void)

{

int i = 0, a, b, ret, user_ret;

char symbol;  0(+), 1(-), 2(*), 3(/)

int count, right = 0;

srand(time(NULL));

while (1) {

a = rand() % 100; 

b = rand() % 100;

symbol = rand() % 4; 

switch (symbol) {

case 0 : {

ret = a + b;

symbol = '+'; 

} break;

case 1 : {

ret = a - b;

symbol = '-';

} break;

case 2 : { 

ret = a * b;

symbol = '*';

} break;

case 3 : { 

ret = a / b;

symbol = '/';

}

}

printf("%d%c%d=", a, symbol, b);

count = 0;

while (1) {

scanf("%d", &user_ret);

if (user_ret == ret) { 

printf("回答正确\n");

right ++; 

break; 

}

printf("错误,再次输入:");

count++; // 答错计数+1

if (count == 3) { 

printf("正确答案是:%d\n", ret);

break; 

}

}

i++; 

printf("是否继续(y/n)?\n");

getchar(); 

scanf("%c", &symbol);

if (symbol != 'y' && symbol != 'Y') 

break;

}

printf("练习结束, 共做题%d, 正确%d, 正确率%.2f%%\n", i, right, (double)right / i * 100);

return 0;

}