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  • 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
    class Solution {
    public:
        bool isHappy(int n) {
            if(n<=0){
                return false;
            }
            unordered_set<int> uset;
            int squareSum = 0;
            while(squareSum!=1){
                squareSum = 0;
                while(n){
                    squareSum += (n%10)*(n%10);
                    n /= 10;
                }
                n = squareSum ;
                if(uset.find(n)!=uset.end()){
                    return false;
                }
                uset.insert(n);
            }
            return true;
        }
    };
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  • 原文地址:https://www.cnblogs.com/zengzy/p/5002290.html
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