human_readable_duration.cpp

#include <string>
#include <sstream>
#include <vector>
#include <iomanip>

std::string human_readable_duration(int num_seconds) {
    std::stringstream buf;
    if (num_seconds < 60) {
        buf << num_seconds << " seconds";
    } else {
        std::vector<int> components;
        while (num_seconds > 0) {
            int comp = num_seconds % 60;
            components.push_back(comp);
            num_seconds /= 60;
        }
        std::vector<int>::const_reverse_iterator iter = components.rbegin();
        buf << *(iter++);
        for (; iter != components.rend(); ++iter) {
            buf << ":" << setw(2) << setfill('0') << *iter;
        }
    }
    return buf.str();
}