title: Count Pairs Difference Equal K
signature: function countPairsDifferenceEqualK(arr: Array<number>, n: number, k: number): number {
test_code: 
  
  // SOLUTION CODE
  // ============================================
  PLACEHOLDER_CODE_BODY
  
  // TESTING CODE 
  // ============================================
  function convertToString(value: any): string{
      return JSON.stringify(value, function (key, val) {
          if (val instanceof Set) {
              return Array.from(val);
          } return val;});
  }
  
  function validateSolution(actual: number, expected: number): boolean {
      return convertToString(actual) === convertToString(expected);
  }
  
  function driver(arr: Array<number>, n: number, k: number, expected:number): string {
      try{
          if (validateSolution(PLACEHOLDER_FN_NAME(arr, n, k),expected)){
              return "PASSED";
          }
          return "FAILED";
      } catch (error) {
        return error.name;
      }
      
  }
      
  function main(){
    let result = '';
    result = driver([9, 14, 17, 19, 22, 23, 23, 27, 30, 31, 34, 37, 37, 39, 39, 42, 57, 61, 68, 73, 77, 79, 91, 96, 97], 19, 19, 3);
    console.log(`TEST-0...${result}`);
  
    result = driver([-78, -42, 28, -88, 18, -52], 3, 4, 0);
    console.log(`TEST-1...${result}`);
  
    result = driver([0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1], 16, 14, 0);
    console.log(`TEST-2...${result}`);
  
    result = driver([8, 46, 57, 28, 80, 2, 75, 57, 83, 45, 32, 49, 77, 30, 94, 33, 23, 29, 35, 81, 85], 15, 11, 3);
    console.log(`TEST-3...${result}`);
  
    result = driver([-90, -72, -72, -62, -62, -54, -54, -52, -48, -38, -22, -22, -22, -12, -12, -8, -8, -8, -6, -6, -2, 6, 12, 26, 26, 28, 28, 38, 40, 48, 52, 52, 58, 60, 68, 70, 72, 76, 76, 76, 92], 22, 25, 0);
    console.log(`TEST-4...${result}`);
  
    result = driver([0, 0, 1, 1, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 1, 0, 0, 1, 0, 1], 45, 39, 0);
    console.log(`TEST-5...${result}`);
  
    result = driver([3, 13, 19, 23, 27, 32, 49, 52, 54, 57, 58, 58, 63, 67, 68, 68, 69, 70, 75, 80, 86, 90, 91, 95], 19, 21, 2);
    console.log(`TEST-6...${result}`);
  
    result = driver([-56, 40, -66, 42, 8, -40, -8, -42], 7, 6, 0);
    console.log(`TEST-7...${result}`);
  
    result = driver([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], 16, 28, 0);
    console.log(`TEST-8...${result}`);
  
    result = driver([99, 12, 90, 10, 86, 86, 81, 19, 1, 1, 98, 82, 34, 39, 34, 1, 54, 47, 39, 82, 21, 50, 82, 41, 98, 47, 88, 46, 72, 28, 28, 29, 60, 87, 92, 53, 93, 29, 74, 75, 11, 32, 48, 47, 85, 16, 20], 24, 45, 3);
    console.log(`TEST-9...${result}`);
  
  };
  
  main();
source_py: def count_pairs_difference_equal_k(arr, n, k):
      count = 0
      for i in range(0, n):
          for j in range((i + 1), n):
              if (((arr[i] - arr[j]) == k) or ((arr[j] - arr[i]) == k)):
                  count += 1
      return count
source_cpp: int count_pairs_difference_equal_k(vector<int> arr, int n, int k) {
    int count = 0;
    for ( int i = 0;
    i < n;
    i ++ ) {
      for ( int j = i + 1;
      j < n;
      j ++ ) if ( arr [ i ] - arr [ j ] == k || arr [ j ] - arr [ i ] == k ) count ++;
    }
    return count;
  }