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/*
Challenge 100
TASK #1 > Fun Time
Submitted by: Mohammad S Anwar
You are given a time (12 hour / 24 hour).
Write a script to convert the given time from 12 hour format to 24 hour format
and vice versa.
Ideally we expect a one-liner.
Example 1:
Input: 05:15 pm or 05:15pm
Output: 17:15
Example 2:
Input: 19:15
Output: 07:15 pm or 07:15pm
*/
#include <iostream>
#include <iomanip>
#include <sstream>
#include <cctype>
class Time {
public:
Time(int hours = 0, int minutes = 0)
: m_hours(hours), m_minutes(minutes), m_is12(false) {}
int hours() const { return m_hours; }
int minutes() const { return m_minutes; }
bool is12() const { return m_is12; }
void set12() { m_is12 = true; }
void set24() { m_is12 = false; }
friend std::ostream& operator<<(std::ostream& os, const Time& time);
friend std::istream& operator>>(std::istream& is, Time& time);
private:
int m_hours, m_minutes; // always in 24 hour format
bool m_is12;
};
std::ostream& operator<<(std::ostream& os, const Time& time) {
if (time.m_is12) {
int hours = time.m_hours;
bool ispm = false;
if (hours == 0)
hours = 12;
else if (hours == 12)
ispm = true;
else if (hours > 12) {
ispm = true;
hours -= 12;
}
os << std::setw(2) << std::setfill('0') << hours << ":"
<< std::setw(2) << std::setfill('0') << time.m_minutes
<< (ispm ? "pm" : "am");
}
else
os << std::setw(2) << std::setfill('0') << time.m_hours << ":"
<< std::setw(2) << std::setfill('0') << time.m_minutes;
return os;
}
std::istream& operator>>(std::istream& is, Time& time) {
// get hh:mm
char colon = '\0';
if (!(is >> time.m_hours >> colon >> time.m_minutes) || colon != ':') {
std::cerr << "error parsing time" << std::endl;
exit(EXIT_FAILURE);
}
// get optional am|pm
std::string ampm;
is >> ampm;
// convert from 12 to 24 format
if (!ampm.empty()) {
switch (tolower(ampm[0])) {
case 'a':
if (time.m_hours == 12) time.m_hours = 0;
time.m_is12 = true;
break;
case 'p':
if (time.m_hours != 12) time.m_hours += 12;
time.m_is12 = true;
break;
default:
std::cerr << "error parsing time" << std::endl;
exit(EXIT_FAILURE);
}
}
return is;
}
int main(int argc, char* argv[]) {
if (argc != 2) {
fputs("Usage: ch-1 time", stderr);
return EXIT_FAILURE;
}
Time time;
std::stringstream ss(argv[1]);
ss >> time;
if (time.is12())
time.set24();
else
time.set12();
std::cout << time << std::endl;
}
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