Why is this program going into an infinite loop after the first scanf?

Question

I am trying to get the program to allow the user to input a number and then have the computer tell the user if the number is too small, too big, or equal to a randomly generated number. The prompt and input work, but it gets stuck after the first scanf.

I think it has to do with scanf and not the conditionals, because I added printf("Testing stopping point") and that doesn't get printed to the user's screen. What am I doing wrong?

#include <stdio.h>
#include <stdbool.h>
#include <time.h>
#include <stdlib.h>

int main()
{
        //Generate a random number
        int n = 1;
        int count = 0;
        int randomNumber;
        srand(time(NULL));

        for (int i = 1; i <= n; i++)
        {
                randomNumber = rand() % 101;
        }

        printf("Guess a number between 1 - 100: ");

        int input;
        scanf("%d\n",&input);

        printf("Testing stopping point");

        do
        {
            if (input > randomNumber)
            {
                count +=1;
                printf("Too large!Try again: ");
                getchar();
            }else if (input < randomNumber)
            {
                count += 1;
                printf("Too small!Try again: ");
                getchar();
            }
        }while (input != randomNumber);

        if(input == randomNumber)
        {
            count +=1;
            printf("Correct!\n");
            printf("You guessed %d times\n", count);
            return 0;
        }
}

Why are you using goto? You can accomplish this all within the do-while loop. — SuperStormer
@SuperStormer thanks. I removed it. I added it when I thought there might have been something wrong with the logic in my do while loop, but it didn't fix the problem — Learning2Code4Life
you dont scanf again so input always says the same. also the last if is redundant — TruVortex_07
No, you need to restructure the loop if you removed the goto — SuperStormer
@Learning2Code4Life put the scanf at the start of the do { [...] } while (); — TruVortex_07

zazz zazz · Accepted Answer · 2021-03-27T00:18:22

You have to remove the \n in the scanf,try like this:

#include <stdio.h>
#include <stdbool.h>
#include <time.h>
#include <stdlib.h>

int main()
{
        //Generate a random number
        
        int count = 0;
        int randomNumber;
        srand(time(NULL));
        randomNumber = (rand() % 101)+1;
        int input=-1;
      
        while (input != randomNumber)
        {
              printf("Guess a number between 1 - 100: ");
             scanf("%d",&input);
            if (input > randomNumber)
            {
                count +=1;
                printf("Too large!Try again: ");
                
            }else if (input < randomNumber)
            {
                count += 1;
                printf("Too small!Try again: ");
               
            }
         
        }
if(input == randomNumber)
        {
            count +=1;
            printf("Correct!\n");
            printf("You guessed %d times\n", count);
           
        }

       return 0; 
}

Why is this program going into an infinite loop after the first scanf?

1 Answers