Happy number (#216)

* add happy number

* impl happy number

leetcode-cc/HappyNumber.hpp

@@ -0,0 +1,54 @@
+#include <unordered_set>
+
+#include "TestHelper.h"
+#include "problem.h"
+#include "solution.h"
+
+using namespace std;
+
+IMPLEMENT_PROBLEM_CLASS(
+    PHappyNumber, 202, DIFFI_EASY, TOPIC_ALGORITHMS, "Harry Number",
+    "Write an algorithm to determine if a number n is happy.", {"Math"});
+
+class SHappyNumber : public ISolution {
+ public:
+  size_t problemId() const override { return 202; }
+  string name() const override {
+    return ("Solution for " + string("Happy Number"));
+  }
+  string location() const override { return __FILE_NAME__; }
+  int test() const override {
+    return testHelper<int, bool>({19, 2}, {true, false}, [this](auto input) {
+      return this->isHappy(input);
+    });
+  };
+  int benchmark() const override { return 0; }
+
+ private:
+  bool isHappy(int n) const {
+    unordered_set<int> memo = {};
+    return check(n, memo);
+  }
+
+  static bool check(int n, unordered_set<int>& memo) {
+    if (n == 1) {
+      return true;
+    } else if (memo.contains(n)) {
+      return false;
+    } else {
+      memo.insert(n);
+      return check(calNum(n), memo);
+    }
+  }
+
+  static int calNum(int n) {
+    int res = 0;
+
+    while (n > 0) {
+      res += pow(n % 10, 2);
+      n /= 10;
+    }
+
+    return res;
+  }
+};

runtime-cc/src/registration.cc

@@ -39,6 +39,7 @@
 #include "../leetcode-cc/FractionToDecimal.hpp"
 #include "../leetcode-cc/GenerateParentheses.hpp"
 #include "../leetcode-cc/GrayCode.hpp"
+#include "../leetcode-cc/HappyNumber.hpp"
 #include "../leetcode-cc/HouseRobber.hpp"
 #include "../leetcode-cc/InsertDeleteGetrandomO1.hpp"
 #include "../leetcode-cc/InsertionSortList.hpp"
@@ -826,5 +827,10 @@ const int registerAll(std::shared_ptr<Container> handle) {
     return std::make_shared<SBitWiseANDOfNumRange>();
   });
 
+  handle->registerProblem(
+      []() -> ArcProblem { return std::make_shared<PHappyNumber>(); });
+  handle->registerSolution(
+      []() -> ArcSolution { return std::make_shared<SHappyNumber>(); });
+
   return 0;
 }