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Decode the Coding Interview in Ruby: Real-World Examples

Angle Between the Hands of a Clock

Understand how to calculate the smaller angle between a clock's hour and minute hands by analyzing their movements. This lesson teaches you to apply formulas that combine hour and minute positions and return the minimal angle, all in constant time and space complexity. You'll gain the skills to translate real-world time into precise geometric calculations.

We'll cover the following...

Description

Given two numbers, hour and minutes we will return the smaller angle (in degrees) formed between the hour and the minute hands on a clock.

Let’s look at some examples to better understand this:

Coding exercise

Ruby
def clock_angle(hour, minutes)
    
    # Your code goes here
    
    return 0.1 # Change the return value as per your requirement
end
Angle Between the Hands of a Clock exercise

Solution

The idea is to separately calculate the angles between the 0-minutes vertical line and each hand. The answer will be the difference that is found between the two angles.

Note: Black lines in the clock represent the 0-minutes vertical lines.

Minute hand angle

Let’s start from the minute hand. The minute hand moves with 1 min intervals. At 1 min, the angle of the minute hand is 6°. . Since the whole circle of the clock is equal to 360° degrees and 60 minutes, we estimated that the minute hand moves 1 min = 360° / 60 = 6° degree with each minute.

Now, we can easily find an angle between the 0-minutes vertical line and a minute hand, using minutes_angle = minutes X 6°. ...