title: Find The Missing Number 2
signature: int findTheMissingNumber2(vector<int> a, 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> a, int n, int expected){
      try
      {
          if (validateSolution(PLACEHOLDER_FN_NAME(a, 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({2, 5, 7, 8, 10, 14, 27, 32, 51, 52, 57, 58, 65, 68, 68, 72, 73, 73, 83, 92, 98}, 12, 50); 
      cout << "TEST-" << 0 << "..."
           <<  result
           << "\n";
  
      result = driver({-60, -48, 38, -78, 88, 86, -4, -94, 16, -64, 32, 88, 58, -78, -16, 48, 38, 30, 66, -60, 20, 40, -28, -64, -48, -86, -80, -8, -58, 52, 80, -32, 46, -4, -70, 76, -4, 78, -64, 38, -40}, 28, -91); 
      cout << "TEST-" << 1 << "..."
           <<  result
           << "\n";
  
      result = driver({0, 0, 0, 0, 0, 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, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1}, 38, 1); 
      cout << "TEST-" << 2 << "..."
           <<  result
           << "\n";
  
      result = driver({69, 59, 22, 33, 69, 28, 11, 34, 72, 88, 16, 30, 69, 89, 43, 4, 65, 85, 27}, 13, 109); 
      cout << "TEST-" << 3 << "..."
           <<  result
           << "\n";
  
      result = driver({-98, -98, -92, -88, -88, -82, -74, -70, -68, -60, -60, -48, -38, -34, -34, -24, 14, 38, 50, 58, 62, 64, 64, 68, 76, 78, 78, 86, 88, 90, 92, 98, 98}, 23, 94); 
      cout << "TEST-" << 4 << "..."
           <<  result
           << "\n";
  
      result = driver({0, 1, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0, 1, 1, 1, 0, 1, 0, 0, 0, 0, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 1, 0, 0}, 41, 42); 
      cout << "TEST-" << 5 << "..."
           <<  result
           << "\n";
  
      result = driver({1, 9, 12, 12, 24, 25, 33, 33, 36, 39, 46, 48, 48, 52, 52, 53, 57, 69, 71, 72, 75, 76, 78, 80, 82, 86, 89, 91, 94, 95, 96, 97, 98, 99}, 30, 124); 
      cout << "TEST-" << 6 << "..."
           <<  result
           << "\n";
  
      result = driver({62, -66, 60, -92, 46, 6, -52, 48, 72, -64, 34, 20, 50, 70, -34, 20, -70, 14, -44, 66, -70}, 17, 101); 
      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, 1}, 30, 0); 
      cout << "TEST-" << 8 << "..."
           <<  result
           << "\n";
  
      result = driver({33, 10, 6, 71, 18, 22, 15, 57, 56, 63, 35, 93, 31, 43, 98, 99, 62, 39, 44, 86, 78, 95, 6, 76, 71}, 12, 32); 
      cout << "TEST-" << 9 << "..."
           <<  result
           << "\n";
  
      return 0;
  }
source_py: def find_the_missing_number_2(a, n):
      x1 = a[0]
      x2 = 1
      for i in range(1, n):
          x1 = (x1 ^ a[i])
      for i in range(2, (n + 2)):
          x2 = (x2 ^ i)
      return (x1 ^ x2)
source_cpp: int find_the_missing_number_2(vector<int> a, int n) {
    int x1 = a [ 0 ];
    int x2 = 1;
    for ( int i = 1;
    i < n;
    i ++ ) x1 = x1 ^ a [ i ];
    for ( int i = 2;
    i <= n + 1;
    i ++ ) x2 = x2 ^ i;
    return ( x1 ^ x2 );
  }