Fraction to decimal (#197)

* add fraction to decimal

* impl fraction to decimal

leetcode-cc/FractionToDecimal.hpp

@@ -0,0 +1,68 @@
+#include <unordered_map>
+
+#include "TestHelper.h"
+#include "problem.h"
+#include "solution.h"
+
+using namespace std;
+
+IMPLEMENT_PROBLEM_CLASS(
+    PFractionToDecimal, 166, DIFFI_MEDIUM, TOPIC_ALGORITHMS,
+    "Fraction to Recurring Decimal",
+    "Given two integers representing the numerator and denominator of a "
+    "fraction, return the fraction in string format.",
+    {""});
+
+class SFractionToDecimal : public ISolution {
+ public:
+  size_t problemId() const override { return 166; }
+  string name() const override {
+    return ("Solution for " + string("Fraction To Recurring Decimal"));
+  }
+  string location() const override { return __FILE_NAME__; }
+  int test() const override {
+    return testHelper<pair<int, int>, string>(
+        {{1, 2}, {2, 1}, {4, 333}}, {"0.5", "2", "0.(012)"},
+        [this](auto input) {
+          return this->fractionToDecimal(input.first, input.second);
+        });
+  };
+  int benchmark() const override { return 0; }
+
+ private:
+  string fractionToDecimal(int numerator, int denominator) const {
+    if (numerator == 0) return "0";
+
+    string result;
+
+    if ((numerator < 0) ^ (denominator < 0)) result += '-';
+
+    long long num = abs((long long)numerator);
+    long long den = abs((long long)denominator);
+
+    result += to_string(num / den);
+
+    long long remainder = num % den;
+    if (remainder == 0) return result;
+
+    result += '.';
+
+    unordered_map<long long, int> map;
+    while (remainder != 0) {
+      // begin recurring
+      if (map.find(remainder) != map.end()) {
+        result.insert(map[remainder], "(");
+        result += ')';
+        break;
+      }
+
+      map[remainder] = result.size();
+
+      remainder *= 10;
+      result += to_string(remainder / den);
+      remainder %= den;
+    }
+
+    return result;
+  }
+};

runtime-cc/src/registration.cc

@@ -28,6 +28,7 @@
 #include "../leetcode-cc/FindPlayersWithZeroOrOneLosses.hpp"
 #include "../leetcode-cc/FlattenBTreeToLinkedList.hpp"
 #include "../leetcode-cc/FourSum.hpp"
+#include "../leetcode-cc/FractionToDecimal.hpp"
 #include "../leetcode-cc/GenerateParentheses.hpp"
 #include "../leetcode-cc/GrayCode.hpp"
 #include "../leetcode-cc/HouseRobber.hpp"
@@ -711,5 +712,10 @@ const int registerAll(std::shared_ptr<Container> handle) {
   handle->registerSolution(
       []() -> ArcSolution { return std::make_shared<SCmpVersionNum>(); });
 
+  handle->registerProblem(
+      []() -> ArcProblem { return std::make_shared<PFractionToDecimal>(); });
+  handle->registerSolution(
+      []() -> ArcSolution { return std::make_shared<SFractionToDecimal>(); });
+
   return 0;
 }