title: Count Pairs Difference Equal K 1
signature: def countPairsDifferenceEqualK1(arr: List[Int], n: Int, k: Int) = {
test_code: import scala.collection.mutable.HashMap
  import scala.collection.immutable.HashSet
  
  
  // SOLUTION CODE
  // ============================================
  PLACEHOLDER_CODE_BODY
  
  
  // TESTING CODE 
  // ============================================
  def validateSolution(actual: Int , expected: Int): Boolean = {
      actual.toString == expected.toString
  }
  
  def driver(arr: List[Int], n: Int, k: Int, expected: Int): String = {
      try {
          if (validateSolution(PLACEHOLDER_FN_NAME(arr, n, k),expected)) {
              "PASSED"
          } else{
              "FAILED"
          }
      }catch{
          case e: Exception => {e.getClass.getName}
      }
  
  }
  object QuestionEvaluator extends App {
  
      println(s"TEST-0...${driver(
        List(5, 5, 10, 19, 29, 32, 40, 60, 65, 70, 72, 89, 92), 7, 12, 
        0    
      )}")   
  
  
      println(s"TEST-1...${driver(
        List(-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    
      )}")   
  
  
      println(s"TEST-2...${driver(
        List(0, 0, 1), 1, 1, 
        0    
      )}")   
  
  
      println(s"TEST-3...${driver(
        List(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    
      )}")   
  
  
      println(s"TEST-4...${driver(
        List(-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    
      )}")   
  
  
      println(s"TEST-5...${driver(
        List(0, 1, 1), 2, 1, 
        1    
      )}")   
  
  
      println(s"TEST-6...${driver(
        List(11, 43, 50, 58, 60, 68, 75), 4, 4, 
        0    
      )}")   
  
  
      println(s"TEST-7...${driver(
        List(-80, -56, -10, 0, 6, 8, 24, 42, 52, 86, 88, 94), 11, 9, 
        0    
      )}")   
  
  
      println(s"TEST-8...${driver(
        List(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    
      )}")   
  
  
      println(s"TEST-9...${driver(
        List(4, 7, 9, 9, 14, 34, 34, 36, 50, 54, 80, 81, 99), 9, 8, 
        0    
      )}")   
  
  }
  
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;
  }