C language classic exercises

Input a character from the terminal and output , Until I met ’q’ end ：

// Input a character from the terminal and output , Until I met 'q' end 
#include <stdio.h>
int main(int argc, char const *argv[])
{
    
    char i;
    while (1)
    {
    
        scanf("%c", &i);
        if (i == '\n')
            continue;
        if (i == 'q')
            break;
        printf("%c\n", i);
    }

    return 0;
}

Loop in a 5 digit , Judge whether it is palindrome number . When the input 0 When the cycle ends .
such as 12321 It's palindrome number , One digit is the same as ten thousand , Ten is the same as one thousand .

// Loop in a 5 digit , Judge whether it is palindrome number . When the input 0 When the cycle ends .
// namely 12321 It's palindrome number , One digit is the same as ten thousand , Ten is the same as one thousand .
#include <stdio.h>
int main(int argc, char const *argv[])
{
    
    int num;
    while (1)
    {
    
        scanf("%d", &num);

        if (num > 9999 && num < 100000)
        {
    
            int g = num % 10;
            int s = num / 10 % 10;
            int q = num / 1000 % 10;
            int w = num / 10000;

            if (g == w && s == q)
                printf("%d It's palindrome number \n", num);
            else
                printf("%d Not palindrome \n", num);
        }
        else if (0 == num)
        {
    
            break;
        }
        else
        {
    
            printf(" Please enter the correct number ！\n");
        }
    }
    return 0;
}

Calculate the size of the array ：

#include <stdio.h>
int main(int argc, char const *argv[])
{
    
    int a[5] = {
    0};
    printf("%d", sizeof(a));
    return 0;
}

Before calculating the Fibonacci sequence 15 Items are output in reverse order
1 1 2 3 5 8 13 21 …
From 3 A start , The first two terms add up to the third term

// Before calculating the Fibonacci sequence 15 Items are output in reverse order 
// 1 1 2 3 5 8 13 21 ...
// From 3 A start , The first two terms add up to the third term 
#include <stdio.h>
int main(int argc, char const *argv[])
{
    
    int arr[15] = {
    1, 1};
    for (int i = 2; i < 15; i++)
    {
    
        arr[i] = arr[i - 1] + arr[i - 2];
    }
    for (int i = 14; i >= 0; i--)
    {
    
        printf("%d ", arr[i]);
    }
    return 0;
}

Enter a string of characters , Calculate the number of spaces

// Enter a string of characters , Calculate the number of spaces 
#include <stdio.h>
int main(int argc, char const *argv[])
{
    
    int sum = 0;
    char s[100] = "";
    scanf("%[^\n]", s);
    for (int i = 0; i < 100; i++)
    {
    
        if (s[i] == 32)
        {
    
            sum++;
        }
    }
    printf("%d", sum);
    return 0;
}