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
1^2 + 9^2 = 82 8^2 + 2^2 = 68 6^2 + 8^2 = 100 1^2 + 0^2 + 0^2 = 1
class Solution { public: int sum_s(int n) { int sum = 0; while(n) { sum+=pow(n%10,2); n/=10; } return sum; } bool isHappy(int n) { int num = n; vector<int>vec; vec.clear(); if(num==1) return true; while(num<INT_MAX) { if(find(vec.begin(),vec.end(),num)==vec.end()) vec.push_back(num); else return false;//同计算循环小数一样, 如果出现循环, 则无需继续计算,直接返回false即可. num = sum_s(num); if(num==1) return true; } return false; } };