LeetCode in TypeScript
202. Happy Number
Easy
Write an algorithm to determine if a number n is happy.
A happy number is a number defined by the following process:
- Starting with any positive integer, replace the number by the sum of the squares of its digits.
- 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.
Return true if n is a happy number, and false if not.
Example 1:
Input: n = 19
Output: true
Explanation:
12 + 92 = 82
82 + 22 = 68
62 + 82 = 100
12 + 02 + 02 = 1
Example 2:
Input: n = 2
Output: false
Constraints:
1 <= n <= 231 - 1
Solution
function isHappy(n: number): boolean {
let a = n
let rem: number
let sum = 0
if (a === 1 || a === 7) {
return true
} else if (a > 1 && a < 10) {
return false
} else {
while (a !== 0) {
rem = a % 10
sum += rem * rem
a = Math.floor(a / 10)
}
return sum === 1 ? true : isHappy(sum)
}
}
export { isHappy }