title: Count Possible Groups Size 2 3 Sum Multiple 3
signature: def countPossibleGroupsSize23SumMultiple3(arr: List[Int], n: Int) = {
test_code: import scala.collection.mutable.HashMap
  import scala.collection.immutable.HashSet
  
  
  // SOLUTION CODE
  // ============================================
  PLACEHOLDER_CODE_BODY
  
  
  // TESTING CODE 
  // ============================================
  def validateSolution(actual: Float , expected: Float): Boolean = {
      (actual - expected).abs < 1e-06F
  }
  
  def driver(arr: List[Int], n: Int, expected: Float): String = {
      try {
          if (validateSolution(PLACEHOLDER_FN_NAME(arr, n),expected)) {
              "PASSED"
          } else{
              "FAILED"
          }
      }catch{
          case e: Exception => {e.getClass.getName}
      }
  
  }
  object QuestionEvaluator extends App {
  
      println(s"TEST-0...${driver(
        List(1, 3, 6, 12, 18, 31, 36, 43, 47, 59, 64, 64, 69, 69, 94, 98, 98), 12, 
        90.0F    
      )}")   
  
  
      println(s"TEST-1...${driver(
        List(94, 46, 64, 18, 70, 22, -98, 52, -26, 34, -22, 22, 40, 66, -72, -66, 86, 84, 12, -38, 28, -60, -10, -30, -78, 76, 62, 74, 24, -64, 0, 92, -20, -66, -52), 23, 
        655.0F    
      )}")   
  
  
      println(s"TEST-2...${driver(
        List(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1), 29, 
        3276.0F    
      )}")   
  
  
      println(s"TEST-3...${driver(
        List(68, 96, 74, 38, 70, 70), 5, 
        7.0F    
      )}")   
  
  
      println(s"TEST-4...${driver(
        List(-88, -74, -70, -64, -64, -64, -58, -52, -18, -10, -6, 4, 4, 28, 44, 48, 52, 54, 64, 72, 76, 94), 18, 
        329.0F    
      )}")   
  
  
      println(s"TEST-5...${driver(
        List(0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0, 1, 1, 1, 1, 1, 0, 0, 1, 0, 0, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 1, 0, 0, 1), 36, 
        2310.0F    
      )}")   
  
  
      println(s"TEST-6...${driver(
        List(9, 12, 14, 21, 27, 28, 45, 50, 54, 57, 58, 62, 78, 82, 91, 92, 95), 9, 
        49.0F    
      )}")   
  
  
      println(s"TEST-7...${driver(
        List(16, -46, -32, -36, -84, -14, -18, 16, 54, 90, -4), 8, 
        24.0F    
      )}")   
  
  
      println(s"TEST-8...${driver(
        List(0, 0, 1, 1), 3, 
        1.0F    
      )}")   
  
  
      println(s"TEST-9...${driver(
        List(53, 32, 54, 84, 79, 37, 44, 30, 92, 53, 89, 95), 8, 
        29.0F    
      )}")   
  
  }
  
source_py: def count_possible_groups_size_2_3_sum_multiple_3(arr, n):
      c = [0, 0, 0]
      res = 0
      for i in range(0, n):
          c[(arr[i] % 3)] += 1
      res += ((c[0] * (c[0] - 1)) >> 1)
      res += (c[1] * c[2])
      res += (((c[0] * (c[0] - 1)) * (c[0] - 2)) / 6)
      res += (((c[1] * (c[1] - 1)) * (c[1] - 2)) / 6)
      res += (((c[2] * (c[2] - 1)) * (c[2] - 2)) / 6)
      res += ((c[0] * c[1]) * c[2])
      return res
source_cpp: int count_possible_groups_size_2_3_sum_multiple_3(vector<int> arr, int n) {
    int c [ 3 ] = {
      0 },
      i;
      int res = 0;
      for ( i = 0;
      i < n;
      i ++ ) c [ arr [ i ] % 3 ] ++;
      res += ( ( c [ 0 ] * ( c [ 0 ] - 1 ) ) >> 1 );
      res += c [ 1 ] * c [ 2 ];
      res += ( c [ 0 ] * ( c [ 0 ] - 1 ) * ( c [ 0 ] - 2 ) ) / 6;
      res += ( c [ 1 ] * ( c [ 1 ] - 1 ) * ( c [ 1 ] - 2 ) ) / 6;
      res += ( ( c [ 2 ] * ( c [ 2 ] - 1 ) * ( c [ 2 ] - 2 ) ) / 6 );
      res += c [ 0 ] * c [ 1 ] * c [ 2 ];
      return res;
    }