【LeetCode】202. Happy Number

问题描述

Write an algorithm to determine if a number 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, 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.

Example: 19 is a happy number

12 + 92 = 82
82 + 22 = 68
62 + 82 = 100
12 + 02 + 02 = 1

找快乐数

分析

使用集合保存所有生成过的数，如果生成了一样的，则表明陷入循环了，此数不为快乐数。

代码

class Solution {
public:
	
	bool isHappy(int n) {
		set<int> elems;
		int t = n;
		while(t) {
			if(t==1) break;
			int i = 0;
			int j = t;
			while(j) {
				i+= (j%10)*(j%10);
				j/=10;
			}
			t = i;
			if(elems.find(t)!=elems.end()) {
				return false;
			}
			elems.insert(t);
		}
		return true;
	}
}