Thread: Switching 2nd and 4th digit in a double(before comma)

The goal of the program is to switch the 2nd and 4th digit in a double(before comma). Lets say you have 28492.45, it should become 29482.45. The program is working fine. I want to add another option, where the user input is a two digit number(before comma) like 56.78, the 3th and 4th digit should be considered as 5600.78. The switched number should be then 5006. Same goes for a 3 digit number. How can i implement this?

Code:

int main() {

    
    double number;
    
    
    scanf("%lf", &number);
    
    //printf("%.4f", number);
    
    char arr[sizeof(number)];
    snprintf(arr, sizeof(number) + 1, "%f", number);
    
    char aux = arr[1];
    arr[1] = arr[3];
    arr[3] = aux;


    number = atof(arr);
    printf("%.4f\n", number);
    
    
    return 0;
}

Originally Posted by Mario F.

The l modifier has no effect on f. It is permitted but does nothing. If you wish to read a long double, you need an uppercase l (i.e. "%Lf").

However, the variable number is a double. "%f" reads doubles, not floats as its name may imply. There is no identifier for floats because floating-point values are always read as double and then converted to float if that is the type of the variable to store the input.

So, in your code, regardless of number being a float or double, you just need "%f". And you would need "%Lf" is the variable was long double.

You're thinking of printf, where floats are converted to double for printing. But with scanf the %lf format is meaningful (and necessary).

Thanks for helping me out!