solve.cpp

#include <cstdio>
#include <string>
#include <vector>
#include <unordered_set>
using namespace std;
class Solution {
	public:
		bool isHappy(int n) {
			return isHappy1(n);
		}
	private:
		bool isHappy1(int n) {
			unordered_set<int> s;
			if (n == 0)
				return false;
			while (n != 1) {
				s.insert(n);
				n = next(n);
				if (s.find(n) != s.end()) {
					return false;
				}
			}
			return true;
		}
		bool isHappy2(int n) {
			int slow = next(n);
			int fast = next(next(n));
			while (slow != 1 && slow != fast) {
				slow = next(slow);
				fast = next(next(fast));
			}
			return slow == 1;
		}
		int next(int n) {
			int ans = 0;
			while (n) {
				int mod = (n % 10);
				ans += (mod * mod);
				n /= 10;
			}
			return ans;
		}
};
int main(int argc, char **argv)
{
	Solution solution;
	int n;
	while (scanf("%d", &n) != EOF) {
		printf("%d : %d\n", n, solution.isHappy(n));
	}
	return 0;
}