title: Count Index Pairs Equal Elements Array 1
signature: int countIndexPairsEqualElementsArray1(vector<int> arr, int n) {
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 expected){
      try
      {
          if (validateSolution(PLACEHOLDER_FN_NAME(arr, n), 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, 11, 18, 22, 40, 46, 50, 51, 53, 55, 64, 67, 73, 78, 86}, 14, 0); 
      cout << "TEST-" << 0 << "..."
           <<  result
           << "\n";
  
      result = driver({14, -98, 98, 58, -82, 90, -80, -56, -30, -36, -56, -30, -58, 68, 72, -76, 38, -90, -72, 4, -32, 32, -28, 2, 12, -72, 54, 2, 0, -74, 8, 12, 46, 72, -84, -66, 70, 18, 26, 72, -26, 44, -8, 20, -32, -56, 28}, 24, 2); 
      cout << "TEST-" << 1 << "..."
           <<  result
           << "\n";
  
      result = driver({0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1}, 13, 56); 
      cout << "TEST-" << 2 << "..."
           <<  result
           << "\n";
  
      result = driver({93, 23, 62, 64, 31, 78, 99}, 4, 0); 
      cout << "TEST-" << 3 << "..."
           <<  result
           << "\n";
  
      result = driver({-94, -94, -92, -86, -84, -76, -76, -68, -66, -56, -56, -54, -50, -46, -38, -34, -34, -30, -26, -18, -16, 2, 8, 42, 52, 54, 56, 64, 68, 82, 82, 82, 94, 96, 98}, 19, 4); 
      cout << "TEST-" << 4 << "..."
           <<  result
           << "\n";
  
      result = driver({0}, 0, 0); 
      cout << "TEST-" << 5 << "..."
           <<  result
           << "\n";
  
      result = driver({3, 18, 18, 20, 21, 23, 24, 27, 35, 36, 38, 40, 46, 50, 50, 51, 52, 53, 59, 61, 63, 63, 65, 66, 68, 68, 70, 71, 74, 75, 96, 98}, 19, 2); 
      cout << "TEST-" << 6 << "..."
           <<  result
           << "\n";
  
      result = driver({-68, 40, 16, 50, 36, 42, -20, -46, -92, 4, -18, -12, 48, 0, -46, 64, -74, -50, 42, 44, -56, 28, -10, 78, 62, 70, -60, 12, -44, -78}, 23, 2); 
      cout << "TEST-" << 7 << "..."
           <<  result
           << "\n";
  
      result = driver({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}, 30, 211); 
      cout << "TEST-" << 8 << "..."
           <<  result
           << "\n";
  
      result = driver({31, 5}, 1, 0); 
      cout << "TEST-" << 9 << "..."
           <<  result
           << "\n";
  
      return 0;
  }
source_py: def count_index_pairs_equal_elements_array_1(arr, n):
      mp = dict()
      for i in range(n):
          if (arr[i] in mp.keys()):
              mp[arr[i]] += 1
          else:
              mp[arr[i]] = 1
      ans = 0
      for it in mp:
          count = mp[it]
          ans += ((count * (count - 1)) // 2)
      return ans
source_cpp: int count_index_pairs_equal_elements_array_1(vector<int> arr, int n) {
    unordered_map < int, int > mp;
    for ( int i = 0;
    i < n;
    i ++ ) mp [ arr [ i ] ] ++;
    int ans = 0;
    for ( auto it = mp . begin ( );
    it != mp . end ( );
    it ++ ) {
      int count = it -> second;
      ans += ( count * ( count - 1 ) ) / 2;
    }
    return ans;
  }