C 编程 - 循环直到用户输入数字 scanf

Question

我需要帮助检查我的程序的错误。我要求用户输入一个整数，我想检查用户输入是否是一个整数。如果没有，请重复 scanf。

我的代码:

int main(void){

  int number1, number2;
  int sum;

  //asks user for integers to add
  printf("Please enter the first integer to add.");
  scanf("%d",&number1);

  printf("Please enter the second integer to add.");
  scanf("%d",&number2);
  //adds integers
  sum = number1 + number2;

  //prints sum
  printf("Sum of %d and %d = %d \n",number1, number2, sum);

  //checks if sum is divisable by 3
  if(sum%3 == 0){
    printf("The sum of these two integers is a multiple of 3!\n");
  }else {
    printf("The sum of these two integers is not a multiple of 3...\n");
  }
  return 0;
}

Answer 1

scanf 根据您的格式返回已成功读取的项目数。您可以设置一个仅当 scanf("%d", &number2); 返回 1 时退出的循环。然而，技巧是当 scanf 返回零时忽略无效数据，因此代码如下所示:

while (scanf("%d",&number2) != 1) {
    // Tell the user that the entry was invalid
    printf("You did not enter a valid number\n");
    // Asterisk * tells scanf to read and ignore the value
    scanf("%*s");
}

由于您在代码中多次读取数字，请考虑创建一个函数来隐藏此循环，并在 main 中调用此函数两次以避免重复。