title: Count Possible Groups Size 2 3 Sum Multiple 3
signature: func countPossibleGroupsSize23SumMultiple3(arr []int, n int) float64 {
test_code: package main
  
  import (
      "fmt"
      "reflect"
      "math"
      "sort"
  )
  
  // SOLUTION CODE
  // ===================================
  PLACEHOLDER_CODE_BODY
  
  // TESTING CODE
  // ===================================
  func validateSolution(actual float64, expected float64) bool {
      return math.Abs(actual - expected) < 1e-06
  }
  
  func driver(arr []int, n int, expected float64) string {
      if validateSolution(PLACEHOLDER_FN_NAME(arr, n),expected) {
              return "PASSED"
      }
      return "FAILED"
  
  }
  
  func main() {
  
      // Use imports to avoid undefined errors
      var _ = reflect.DeepEqual
      _ = math.Abs
      _ = sort.Sort
      result := ""
      result = driver([]int{1, 3, 6, 12, 18, 31, 36, 43, 47, 59, 64, 64, 69, 69, 94, 98, 98}, 
  	12, 90.0)
      fmt.Printf("TEST-0...%s\n", result)
      
      result = driver([]int{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, 655.0)
      fmt.Printf("TEST-1...%s\n", result)
      
      result = driver([]int{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, 3276.0)
      fmt.Printf("TEST-2...%s\n", result)
      
      result = driver([]int{68, 96, 74, 38, 70, 70}, 
  	5, 7.0)
      fmt.Printf("TEST-3...%s\n", result)
      
      result = driver([]int{-88, -74, -70, -64, -64, -64, -58, -52, -18, -10, -6, 4, 4, 28, 44, 48, 52, 54, 64, 72, 76, 94}, 
  	18, 329.0)
      fmt.Printf("TEST-4...%s\n", result)
      
      result = driver([]int{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, 2310.0)
      fmt.Printf("TEST-5...%s\n", result)
      
      result = driver([]int{9, 12, 14, 21, 27, 28, 45, 50, 54, 57, 58, 62, 78, 82, 91, 92, 95}, 
  	9, 49.0)
      fmt.Printf("TEST-6...%s\n", result)
      
      result = driver([]int{16, -46, -32, -36, -84, -14, -18, 16, 54, 90, -4}, 
  	8, 24.0)
      fmt.Printf("TEST-7...%s\n", result)
      
      result = driver([]int{0, 0, 1, 1}, 
  	3, 1.0)
      fmt.Printf("TEST-8...%s\n", result)
      
      result = driver([]int{53, 32, 54, 84, 79, 37, 44, 30, 92, 53, 89, 95}, 
  	8, 29.0)
      fmt.Printf("TEST-9...%s\n", result)
      
          
  }
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;
    }