验证输入和重复语句

Question

I need to take two numbers from two separate scans and find the GCD of both of them. I have this currently which will take the two numbers, but I need to validate input with a function. It should work as follows, I enter a number and it checks to verify that it is a positive integer. If not it should prompt me to say that the input is unrecognized and ask for it again. Once I input a valid number, it should continue to ask me to put in a second one and do the same verification process. Any help with input validation and repeating the question in a function would be helpful.

int main()
{
    int num1, num2, i, GCD;
   
    printf("Please enter a positive integer: \n");
    scanf("%d" ,&num1);
    printf("Please enter a positive integer:\n");
    scanf("%d", &num2);
if (num1 >0 && num2 > 0) {
    for(i = 1; i <= num1 && i <= num2; i++)
    {
        if(num1 % i == 0 && num2 % i == 0)
            GCD = i;
    }
}
else {
   printf("I'm sorry that number is unrecognized or negative.\n");

}
printf("The largest integer that divides both %d and %d is: %d\n",num1,num2, GCD);

    return 0;
}

Answer 1

you can use a do-while loop and put your scanf in there as long as you dont get a valid answer. For example:

do {

   // put your scans here 

} while(num1<0 || num2<0);

Also you can catch the case if he inputs a character instead of integer input! So that is a good way to repeat a prompt until you get the valid answer.