LeetCode - Happy Number

문제 설명

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

/**
 * @param {number} n
 * @return {boolean}
 */
var isHappy = function(n) {
    
    /*
        이전에 나왔던 숫자가 반복되면 loop인걸 확인할수 있음
    */
    let map=new  Map();

    for(; map.get(n)==null; ){ 
        map.set(n,1);

        let number=n;

        let tempSum=0;
        for(; number>0; ){
            let rest= number%10;
            tempSum=tempSum+Math.pow(rest,2);
           // tempSum=tempSum+ (rest*rest)
            number=(number/10)>>0; //10으로 나눈 몫에 비트연산으로 소수점 절사
        }
        if(tempSum==1){
            return true;
        }
        n=tempSum;
    }
    return false;

};

~.~