title: Triangular Matchstick Number
signature: float triangularMatchstickNumber(int x) {
test_code: #include <algorithm>
  #include <assert.h>
  #include <cstdlib>
  #include <iostream>
  #include <map>
  #include <set>
  #include <string>
  #include <tuple> 
  #include <unordered_map>
  #include <vector>
  #include <math.h>
  #include <cmath>
  #include <bits/stdc++.h>
  #include <numeric>
  #include <functional>
  
  using namespace std;
  
  // SOLUTION CODE
  // ============================================
  PLACEHOLDER_CODE_BODY
  
  // TESTING CODE 
  // ============================================
  bool validateSolution(float actual, float expected){
      return abs(actual - expected) < 1e-06;
  }
  
  string driver(int x, float expected){
      try
      {
          if (validateSolution(PLACEHOLDER_FN_NAME(x), expected)){
              return "PASSED";
          }
          return "FAILED";
      }
      catch (const std::overflow_error& exception_obj)
      {
          return typeid(exception_obj).name();
      }
      catch (const std::runtime_error& exception_obj)
      {
          return typeid(exception_obj).name();
      }
      catch (const std::exception& exception_obj)
      {
          return typeid(exception_obj).name();
      }
      catch (...)
      {
          return "UNK_ERROR";
      }
  }
  
  int main() {
      string result = "";
  
      result = driver(6, 63.0); 
      cout << "TEST-" << 0 << "..."
           <<  result
           << "\n";
  
      result = driver(25, 975.0); 
      cout << "TEST-" << 1 << "..."
           <<  result
           << "\n";
  
      result = driver(15, 360.0); 
      cout << "TEST-" << 2 << "..."
           <<  result
           << "\n";
  
      result = driver(30, 1395.0); 
      cout << "TEST-" << 3 << "..."
           <<  result
           << "\n";
  
      result = driver(17, 459.0); 
      cout << "TEST-" << 4 << "..."
           <<  result
           << "\n";
  
      result = driver(80, 9720.0); 
      cout << "TEST-" << 5 << "..."
           <<  result
           << "\n";
  
      result = driver(27, 1134.0); 
      cout << "TEST-" << 6 << "..."
           <<  result
           << "\n";
  
      result = driver(13, 273.0); 
      cout << "TEST-" << 7 << "..."
           <<  result
           << "\n";
  
      result = driver(12, 234.0); 
      cout << "TEST-" << 8 << "..."
           <<  result
           << "\n";
  
      result = driver(67, 6834.0); 
      cout << "TEST-" << 9 << "..."
           <<  result
           << "\n";
  
      return 0;
  }
source_py: def triangular_matchstick_number(x):
      return (((3 * x) * (x + 1)) / 2)
source_cpp: int triangular_matchstick_number(int x) {
    return ( 3 * x * ( x + 1 ) ) / 2;
  }