title: Count Pairs Difference Equal K 1
signature: int countPairsDifferenceEqualK1(vector<int> arr, int n, int k) {
test_code: #include <algorithm>
  #include <assert.h>
  #include <cstdlib>
  #include <iostream>
  #include <map>
  #include <set>
  #include <string>
  #include <tuple> 
  #include <unordered_map>
  #include <vector>
  #include <math.h>
  #include <cmath>
  #include <bits/stdc++.h>
  #include <numeric>
  #include <functional>
  
  using namespace std;
  
  // SOLUTION CODE
  // ============================================
  PLACEHOLDER_CODE_BODY
  
  // TESTING CODE 
  // ============================================
  bool validateSolution(int actual, int expected){
      return actual == expected;
  }
  
  string driver(vector<int> arr, int n, int k, int expected){
      try
      {
          if (validateSolution(PLACEHOLDER_FN_NAME(arr, n, k), expected)){
              return "PASSED";
          }
          return "FAILED";
      }
      catch (const std::overflow_error& exception_obj)
      {
          return typeid(exception_obj).name();
      }
      catch (const std::runtime_error& exception_obj)
      {
          return typeid(exception_obj).name();
      }
      catch (const std::exception& exception_obj)
      {
          return typeid(exception_obj).name();
      }
      catch (...)
      {
          return "UNK_ERROR";
      }
  }
  
  int main() {
      string result = "";
  
      result = driver({5, 5, 10, 19, 29, 32, 40, 60, 65, 70, 72, 89, 92}, 7, 12, 0); 
      cout << "TEST-" << 0 << "..."
           <<  result
           << "\n";
  
      result = driver({-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); 
      cout << "TEST-" << 1 << "..."
           <<  result
           << "\n";
  
      result = driver({0, 0, 1}, 1, 1, 0); 
      cout << "TEST-" << 2 << "..."
           <<  result
           << "\n";
  
      result = driver({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); 
      cout << "TEST-" << 3 << "..."
           <<  result
           << "\n";
  
      result = driver({-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); 
      cout << "TEST-" << 4 << "..."
           <<  result
           << "\n";
  
      result = driver({0, 1, 1}, 2, 1, 1); 
      cout << "TEST-" << 5 << "..."
           <<  result
           << "\n";
  
      result = driver({11, 43, 50, 58, 60, 68, 75}, 4, 4, 0); 
      cout << "TEST-" << 6 << "..."
           <<  result
           << "\n";
  
      result = driver({-80, -56, -10, 0, 6, 8, 24, 42, 52, 86, 88, 94}, 11, 9, 0); 
      cout << "TEST-" << 7 << "..."
           <<  result
           << "\n";
  
      result = driver({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); 
      cout << "TEST-" << 8 << "..."
           <<  result
           << "\n";
  
      result = driver({4, 7, 9, 9, 14, 34, 34, 36, 50, 54, 80, 81, 99}, 9, 8, 0); 
      cout << "TEST-" << 9 << "..."
           <<  result
           << "\n";
  
      return 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;
  }