LeetCode 刷題: Happy Number 的判斷
阿新 • • 發佈:2019-02-18
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; if(n == 1) return true; unordered_set<int> array; array.insert(n); int s; while(true) { s=0; while(n) { s += (n%10)*(n%10); n /= 10; } if(s == 1) return true; else if(array.find(s) != array.end()) return false; n = s; array.insert(n); } } };