Converting minutes to seconds in C?

[SexayMistahBee]

I'm trying to convert the decimals of minutes as a float to seconds.

So if it were 50.429 minutes, it would be 50 minutes and 25 seconds

I've tried converting the float value to int and subtracting it from the original float and multiplying it by 60

ex)
((50.429-(int)50.429)*60)

but this gives me a 26 seconds instead of 25.

I really need to get back to the basics; what's going on here?

Is there a better way to do this? (without using floor)

thanks :/

 

but this gives me a 26 seconds instead of 25.

I really need to get back to the basics; what's going on here?

Is there a better way to do this? (without using floor)

thanks :/

You can emulate the behaviour of floor using integer division.

	float input = 50.429;
	int m = input / 1;
	int s = ((input - m) * 60) / 1;
	printf("%d %d", m, s);

Look up "integer division" in C for details.

 

[SexayMistahBee]

Thanks, dividing by 1 helped clear up my code a bit.

This was for a simple programming assignment, and here's the product

#include <stdio.h>

int main(void)
{
	float input;
	int hour, min, sec;

	printf("How many minutes did the trains take to meet?\n");
	scanf("%f",&input);

	hour = (int)input/60;
	min = ((int)input/1)%60;
	sec = ((input-(int)input)*60)/1;
	printf("%d hours %dminutes %dseconds\n",hour,min,sec);

	return 0;
}

 

Math.h also has a floor function if you wanted to use standard libraries instead

 

Thanks, dividing by 1 helped clear up my code a bit.

This was for a simple programming assignment, and here's the product

#include <stdio.h>

int main(void)
{
	float input;
	int hour, min, sec;

	printf("How many minutes did the trains take to meet?\n");
	scanf("%f",&input);

	hour = (int)input/60;
	min = ((int)input/1)%60;
	sec = ((input-(int)input)*60)/1;
	printf("%d hours %dminutes %dseconds\n",hour,min,sec);

	return 0;
}

Some tips:
Scanf is a shitty function prone to all sorts of unintended behaviour. You are much better off capturing the input into a buffer then using sscanf. In this case the input is so simple that not much can go wrong, but it's good practice all the same.

For an overflow-safe read from STDIN use fgets:

Fgets -- Reads characters from stream and stores them as a C string into str until (num-1) characters have been read or either a newline or the end-of-file is reached, whichever happens first.

As the manpage says, the fgets function will behave as a read function should: reading up to the number of chars specified, a new line char or EOF, which ever comes first. The function also provides a return value indicating the success of the read. If the read fails (i.e. EOF has been reached or broken pipe etc.) then it returns null.

You should also note that all scanf functions return the number of elements in the format string that they successfully scanned. So for example if you had "%f %f %f" but your input string was "50.0 5.1" then it would return 2.

So for example (untested):

char buffer[51];
if (fgets(buffer, 50, stdin)) {
    float x = 0;
    if (sscanf(buffer, "%f", &x) == 1) {
        // float was read from input do calcs here
    } else {
        fprintf(stderr, "input did not contain a float\n");
    }
} else {
    fprintf(stderr, "read from stdin failed\n");
}