Leetcode 202. Happy Number

202. Happy Number

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

Credits:
Special thanks to @mithmatt and @ts for adding this problem and creating all test cases.

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class Solution {
public:
    int get(int x){    //得到下一个数
        int temp=0;
        while(x){
            temp+=(x%10)*(x%10);
            x/=10;
        }
        return temp;
    }
    bool isHappy(int n) {
        set<int>Q;
        Q.insert(n);
        
        while(1){
            int t=get(n);
            if(t==1){
                return true;
            }
            else{
                if(Q.count(t)){
                    return false;
                }
                else{
                    Q.insert(t);
                }
            }
            n=t;
        }
    }
};

出现1，返回true，如果出现循环, 则无需继续计算,直接返回false即可