202. Happy Number

 1 class Solution {
 2 public:
 3     bool isHappy(int n) {
 4         bool happy = true;
 5         vector<int> digit;
 6         set<int> calc;
 7         while (happy) {
 8             while (n) {
 9                 digit.push_back(n % 10);
10                 n /= 10;
11             }
12             int sum = 0;
13             for (int i = 0; i < digit.size(); ++ i) sum += digit[i]*digit[i];
14             if (sum == 1) break;
15             int count = calc.size();
16             calc.insert(sum);
17             if (count == calc.size()) happy = false;
18             n = sum;
19             digit.clear();
20         }
21         return happy;
22     }
23 };