3.0 KiB
3.0 KiB
title | id | challengeType |
---|---|---|
Happy numbers | 594810f028c0303b75339ad1 | 5 |
Description
A happy number is defined by the following process:
Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1. Those numbers for which this process ends in 1 are happy numbers, while those that do not end in 1 are unhappy numbers.
Implement a function that returns true if the number is happy, or false if not.
Instructions
Tests
tests:
- text: <code>happy</code> is a function.
testString: assert(typeof happy === 'function', '<code>happy</code> is a function.');
- text: <code>happy(1)</code> should return a boolean.
testString: assert(typeof happy(1) === 'boolean', '<code>happy(1)</code> should return a boolean.');
- text: <code>happy(1)</code> should return true.
testString: assert(happy(1), '<code>happy(1)</code> should return true.');
- text: <code>happy(2)</code> should return false.
testString: assert(!happy(2), '<code>happy(2)</code> should return false.');
- text: <code>happy(7)</code> should return true.
testString: assert(happy(7), '<code>happy(7)</code> should return true.');
- text: <code>happy(10)</code> should return true.
testString: assert(happy(10), '<code>happy(10)</code> should return true.');
- text: <code>happy(13)</code> should return true.
testString: assert(happy(13), '<code>happy(13)</code> should return true.');
- text: <code>happy(19)</code> should return true.
testString: assert(happy(19), '<code>happy(19)</code> should return true.');
- text: <code>happy(23)</code> should return true.
testString: assert(happy(23), '<code>happy(23)</code> should return true.');
- text: <code>happy(28)</code> should return true.
testString: assert(happy(28), '<code>happy(28)</code> should return true.');
- text: <code>happy(31)</code> should return true.
testString: assert(happy(31), '<code>happy(31)</code> should return true.');
- text: <code>happy(32)</code> should return true:.
testString: assert(happy(32), '<code>happy(32)</code> should return true:.');
- text: <code>happy(33)</code> should return false.
testString: assert(!happy(33), '<code>happy(33)</code> should return false.');
Challenge Seed
function happy (number) {
// Good luck!
}
Solution
function happy (number) {
let m;
let digit;
const cycle = [];
while (number !== 1 && cycle[number] !== true) {
cycle[number] = true;
m = 0;
while (number > 0) {
digit = number % 10;
m += Math.pow(digit, 2);
number = (number - digit) / 10;
}
number = m;
}
return (number === 1);
}