LEETCODE ALGORITHM:202. Happy Number

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题目

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, 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.

Return True if n is a happy number, and False if not.

Example:

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Input: 19
Output: true
Explanation: 
12 + 92 = 82
82 + 22 = 68
62 + 82 = 100
12 + 02 + 02 = 1

题解

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//set保存出现过的数，找是否为循环
class Solution {
public:
    bool isHappy(int n) {
        int tmp=n,res=0;
        set<int> exists;
        exists.emplace(n);
        while(1)
        {
            while(tmp!=0)
            {
                res+=pow(tmp%10,2);
                tmp/=10;
            }
            tmp=res;res=0;
            if(tmp==1) return true;
            else if(exists.find(tmp)!=exists.end()) return false;
            exists.emplace(tmp);
        }
    }
};