LeetCode:Happy Number
problem:
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
solution: 同循环小数的计算
class Solution { public: bool isHappy(int n) { unordered_set<int> markset; //set存储已出现的数字 if(n<1) return false; if(n==1) return true; markset.insert(n); while(true) { int sum=0; while(n) { sum+=(n%10)*(n%10); n/=10; } if(sum==1) return true; else if(markset.find(sum)!=markset.end()) return false; markset.insert(sum); n=sum; } } };