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
- LeetCode Source
- 分析:如果不是Happy Number的话,在计算过程中会出现loop。所以我们采用一组set来监测是否有loop。
class Solution { public: bool isHappy(int n) { unordered_set<int> s; while(true){ if(n==1) return true; if(s.find(n)!=s.end()) return false; s.insert(n); n = Caculate(n); } } int Caculate(int n){ int ret=0; while(n!=0){ ret+=(n%10)*(n%10); n=n/10; } return ret; } };