What's the problem with this C program about Fibonacci ? Could you help me?-CodePudding

//0、1、1、2、3、5、8、13、21、34
//F(0) = 0，F(1) = 1, F(n) = F(n - 1)   F(n - 2)（n >= 2，n∈N*）
#include <stdio.h>
int Fibonacci(int n);
int get_int(void);
int main(void)
{
    int n, i;
    printf("Please enter the No. (<0 to quit) :\n");
    n = get_int();
    while (scanf("%d", &n) == 1 && n > 0)
    {
        for (i = 1; i <= n; i  )
        {
            printf("%d ", Fibonacci(i));
        }
        printf("\n");
    }
    printf("Done.\n");
    return 0;
}
int Fibonacci(int n)
{
    if (n == 1)
    {
        return 0;
    }
    else if (n == 2)
    {
        return 1;
    }
    else if (n >= 3)
    {
        return Fibonacci(n - 1)   Fibonacci(n - 2);
    }
}
int get_int(void)
{
    int x;
    while (scanf("%d", &x) != 1)
    {
        scanf("%*s");   
        printf("Please enter an integer number(>0):\n");
    }
    while (getchar() != '\n')
        continue;  
    return x;
}

input & output enter image description here As you can see in the picture, when I first enter 8. It does not run anything. Only if I enter 8 again, it could run smoothly. How to modify the code so that when I first enter 8 it could print?

Thanks, justANewbie. I have modified as followsing:

//F(0) = 0，F(1) = 1, F(n) = F(n - 1)   F(n - 2)（n >= 2，n∈N*）
#include <stdio.h>
int Fibonacci(int n);
int get_int(void);
int main(void)
{
    int n, i;
    printf("Please enter the No. (<0 to quit) :\n");
    n = get_int();
    while (n > 0)
    {
        for (i = 1; i <= n; i  )
        {
            printf("%d ", Fibonacci(i));
        }
        printf("\n");
    }
    printf("Done.\n");
    return 0;
}
int Fibonacci(int n)
{
    if (n == 1)
    {
        return 0;
    }
    else if (n == 2)
    {
        return 1;
    }
    else if (n >= 3)
    {
        return Fibonacci(n - 1)   Fibonacci(n - 2);
    }
}
int get_int(void)
{
    int x;
    while ((scanf("%d", &x)) != 1)
    {
        scanf("%*s");  
        printf("Please enter an integer number(>0):\n");
    }
    while (getchar() != '\n')
        continue;  
    return x;
}

The question before has been solved. However, a new problem arises like this: enter image description here

The output hasn't stop. What's the problem?

CodePudding user response：

You declare: n = get_int(); which calls get_int(). In get_int() you ask your user input(by scanf("%*s");) as seen in here:

int get_int(void)
{
    int x;
    while (scanf("%d", &x) != 1)
    {
        scanf("%*s"); // <-- you ask for user input in this line.
        printf("Please enter an integer number(>0):\n");
    }
    while (getchar() != '\n')
        continue;  
    return x;
}

Then, you call scanf() in main() as seen in here:

int main(void)
{
    int n, i;
    printf("Please enter the No. (<0 to quit) :\n");
    n = get_int();
    while (scanf("%d", &n) /* <-- here */ == 1 && n > 0)
    {
        for (i = 1; i <= n; i  )
        {
            printf("%d ", Fibonacci(i));
        }
        printf("\n");
    }
    printf("Done.\n");
    return 0;
}

So you ask for user input 2 times and that cause your error.