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Decode the Coding Interview in JavaScript: Real-World Examples

Angle Between the Hands of a Clock

Understand how to calculate the smaller angle between the hour and minute hands of a clock by separately computing their angles from the vertical line. Learn to implement this using a JavaScript algorithm with constant time and space complexity for coding interview practice.

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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

Javascript (babel-node)
function clockAngle(hour, minutes) {
  // Write your code here
  return 0.1
}
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 minutesAngle = minutes X 6°. ...