clocktest

Clock Angle Problem
BY SJ · FEBRUARY 20, 2015

Objec­tive: Find the Angle between hour hand and minute hand at the given time.

Exam­ple:

Time : 12:45
Input : hour = 12, Minute = 45
Output : 112.5

Time : 3:30
Input : hour = 3, Minute = 30
Output : 75
 Approach:

At 12:00 both hand meet, take it as reference.
Angle between hand and minute = angle of hour hand ~ angle of minute hand.
return minimum(angle, 360-angle)
hour hand moves 360 in 12 hours => 360/12 = 30 degree in one hour or 0.5 degree in 1 min
Minute hand moves 360 in 60 mins => 360/60 = 6 degree in one min
So if given time is h hours and m mins, hour hand will move (h*60+m)*0.5 and minute hand will move 6*m
Code:

public class AngleHourMinute {

	public static double angle(int hour, int minute) {
		if (hour < 0 || minute < 0) {
			return -1;
		}
		if (hour == 12) {
			hour = 0;
		}
		if (minute == 60) {
			minute = 0;
			hour += 1;
		}
		double hourAngle = (hour * 60 + minute) * 0.5;
		double minAngle = minute * 6;
		double bwAngle = Math.abs(hourAngle - minAngle);
		return Math.min(360 - bwAngle, bwAngle);

	}

	public static void main(String[] args) {
		System.out.println(angle(12, 45));
		System.out.println(angle(3, 30));
		System.out.println(angle(2, 23));

	}

}