title: Count Pairs Difference Equal K 1
signature: function countPairsDifferenceEqualK1($arr, $n, $k) {
test_code: <?php
  
  
  // SOLUTION CODE 
  // ============================================
  PLACEHOLDER_CODE_BODY
  
  // TESTING CODE 
  // ============================================
  function validateSolution($actual, $expected){
      return serialize($actual) == serialize($expected);
  }
  
  function driver($arr, $n, $k, $expected){
      try{
        if (validateSolution(PLACEHOLDER_FN_NAME($arr, $n, $k), $expected)){
          return "PASSED";
        }
        return "FAILED";
      }
      catch (Exception $exception_obj) {
        return get_class($exception_obj);
      }
  }
  
  function main(){
      printf("TEST-0...%s\n",driver(
        array(5, 5, 10, 19, 29, 32, 40, 60, 65, 70, 72, 89, 92), 7, 12, 
        0));
      
      printf("TEST-1...%s\n",driver(
        array(-98, -90, -88, -82, -80, -78, -74, -74, -72, -62, -58, -58, -56, -52, -48, -46, -38, -38, -30, -12, -10, 4, 8, 8, 14, 22, 24, 26, 36, 40, 40, 48, 56, 58, 58, 58, 60, 62, 64, 68, 68, 74, 84), 24, 36, 
        7));
      
      printf("TEST-2...%s\n",driver(
        array(0, 0, 1), 1, 1, 
        0));
      
      printf("TEST-3...%s\n",driver(
        array(1, 7, 13, 14, 16, 29, 34, 42, 44, 49, 59, 62, 65, 66, 70, 71, 73, 73, 76, 80, 96, 96), 12, 16, 
        1));
      
      printf("TEST-4...%s\n",driver(
        array(-98, -88, -58, -56, -48, -34, -22, -18, -14, -14, -8, -4, -2, 2, 18, 38, 42, 46, 54, 68, 70, 90, 94, 96, 98), 23, 22, 
        4));
      
      printf("TEST-5...%s\n",driver(
        array(0, 1, 1), 2, 1, 
        1));
      
      printf("TEST-6...%s\n",driver(
        array(11, 43, 50, 58, 60, 68, 75), 4, 4, 
        0));
      
      printf("TEST-7...%s\n",driver(
        array(-80, -56, -10, 0, 6, 8, 24, 42, 52, 86, 88, 94), 11, 9, 
        0));
      
      printf("TEST-8...%s\n",driver(
        array(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), 29, 30, 
        0));
      
      printf("TEST-9...%s\n",driver(
        array(4, 7, 9, 9, 14, 34, 34, 36, 50, 54, 80, 81, 99), 9, 8, 
        0));
      
  }
  
  main();
  ?>
source_py: def count_pairs_difference_equal_k_1(arr, n, k):
      count = 0
      arr.sort()
      l = 0
      r = 0
      while (r < n):
          if ((arr[r] - arr[l]) == k):
              count += 1
              l += 1
              r += 1
          elif ((arr[r] - arr[l]) > k):
              l += 1
          else:
              r += 1
      return count
source_cpp: int count_pairs_difference_equal_k_1(vector<int> arr, int n, int k) {
    int count = 0;
    sort(arr.begin(), arr.end());
    int l = 0;
    int r = 0;
    while ( r < n ) {
      if ( arr [ r ] - arr [ l ] == k ) {
        count ++;
        l ++;
        r ++;
      }
      else if ( arr [ r ] - arr [ l ] > k ) l ++;
      else r ++;
    }
    return count;
  }