C scanf() issues?

问题:

In this simple guess-the-number game, scanf() is not working the second time in main. I would really appreciate if someone could explain why doesn't work and how to fix it. Any tips on how to clean this code up?. Thank you!

#include<stdio.h>
#include<stdlib.h>
#include<time.h>
int guessed = 0;
int guesses = 0;
int total_guesses = 0;
int range_top = 1;
int generate_random_number()
{
    srand(time(NULL));
    return (rand() % range_top);
}
void take_guess(int num)
{
    int guess;
    printf("what is your guess:  ");
    scanf("%i",&guess);
    if(guess == num)
    {
        guessed = 1;
    }
    else if(guess>num)
    {
        printf("Your guess was too high,\n");
    }
    else 
    {
        printf("Your guess was too low.\n");
    }

}
int main(void)
{
    printf("This is a game in C\n");
    printf("Would you like to play? (y/n): ");
    char play;
    scanf("%c",&play);
    while(play == 'y')
    {
        printf("I am thinking of a number between 0 and %i\n",range_top);
        int num = generate_random_number();
        while(guessed ==0)
        {
            take_guess(num);
            guesses++;
        }
        printf("It took you ");
        printf("%i",guesses);
        printf(" guesses to win.\n");
        printf("Would you like to play again? (y/n): ");
        scanf("%c",&play);
        guessed = 0;
        guesses = 0;
        total_guesses+=guesses;

    }
    printf("goodbye!");
}

回答1:

This is a classic newbie error.

scanf("%c",&play);

will read the newline character that is left in the input stream after you read the number in take_guess.

Use

scanf(" %c",&play);

instead.

When you have a whitespace character before %c in the format specifier, the function will read the first non-whitespace character from the input stream. Otherwise, it will read the first available character from the input stream.

回答2:

Before scanf use fflush(stdin)