Task

Write a function or program which:

   takes a positive integer representing a duration in seconds as input (e.g., 100), and
   returns a string which shows the same duration decomposed into:
   weeks,
   days, 
   hours, 
   minutes,   and 
   seconds.
This is detailed below (e.g., "2 hr, 59 sec").



Demonstrate that it passes the following three test-cases:

Test Cases


 input number

 output string


 7259

 2 hr, 59 sec


 86400

 1 d


 6000000

 9 wk, 6 d, 10 hr, 40 min

Details
The following five units should be used:



 unit

 suffix used in output

 conversion


 week

 wk

 1 week = 7 days


 day

 d

 1 day = 24 hours


 hour

 hr

 1 hour = 60 minutes


 minute

 min

 1 minute = 60 seconds


 second

 sec



However, only include quantities with non-zero values in the output (e.g., return "1 d" and not "0 wk, 1 d, 0 hr, 0 min, 0 sec").

Give larger units precedence over smaller ones as much as possible (e.g., return 2 min, 10 sec and not 1 min, 70 sec or 130 sec)

Mimic the formatting shown in the test-cases (quantities sorted from largest unit to smallest and separated by comma+space; value and unit of each quantity separated by space).




/*
 * Program seconds2string, C89 version.
 *
 * Read input from argv[1] or stdin, write output to stdout.
 */
 
#define _CRT_SECURE_NO_WARNINGS /* unlocks printf in Microsoft Visual Studio */
 
#include <stdio.h>
#include <stdlib.h>
 
/*
 * Converting the number of seconds in a human-readable string.
 * It is worth noting that direct output to stdout would be even simpler.
 */
char* seconds2string(unsigned long seconds) 
{
    int i;
 
    const unsigned long s =  1;
    const unsigned long m = 60 * s;
    const unsigned long h = 60 * m;
    const unsigned long d = 24 * h;
    const unsigned long w =  7 * d;
 
    const unsigned long coeff[5] = { w, d, h, m, s };
    const char units[5][4] = { "wk", "d", "hr", "min", "sec" };
 
    static char buffer[256];
    char* ptr = buffer;
 
    for ( i = 0; i < 5; i++ )
    {
        unsigned long value;
        value   = seconds / coeff[i];
        seconds = seconds % coeff[i];
        if ( value )
        {
            if ( ptr != buffer ) 
                ptr += sprintf(ptr, ", ");
            ptr += sprintf(ptr,"%lu %s",value,units[i]);
        }
    }
 
    return buffer;
}
 
/*
 * Main function for seconds2string program.
 */
int main(int argc, char argv[])
{
    unsigned long seconds;
 
    if ( (argc <  2) && scanf( "%lu", &seconds ) 
    ||   (argc >= 2) && sscanf( argv[1], "%lu", & seconds ) )
    {
        printf( "%s\n", seconds2string(seconds) );
        return EXIT_SUCCESS;
    }
 
    return EXIT_FAILURE;
}