title: Find The Missing Number 1
signature: class Solution {
  
      public int FindTheMissingNumber1(List<int> a, int n) {
test_code: using System;
  using System.Numerics;
  using System.Diagnostics;
  using System.Collections.Generic;
  using System.Linq;
  using System.Text;
  using System.Security.Cryptography;
  using System.Web.UI;
  using System.Web.Script.Serialization;
  
  // SOLUTION CODE
  // ============================================
  PLACEHOLDER_CODE_BODY
  
  // TESTING CODE 
  // ============================================
  namespace EvaluatePrediction {
      class TestRunner {
          public bool ValidateSolution(int actual, int expected){
              return new JavaScriptSerializer().Serialize(actual) == new JavaScriptSerializer().Serialize(expected);
          }
  
          public string driver(List<int> a, int n, int expected){
              try{
                PLACEHOLDER_CLS_NAME solution_cls = new PLACEHOLDER_CLS_NAME();
                int pred_result = solution_cls.PLACEHOLDER_FN_NAME(a, n); 
                if (ValidateSolution(
                      pred_result,
                      expected)){
                  return "PASSED";
                }
                return "FAILED";
              } 
              catch (Exception exception_obj)
              {
                return exception_obj.GetType().FullName;
              }
          }
          static void Main(string[] args) {
              TestRunner runner = new TestRunner();
              String result;
              result = runner.driver(
                  new List<int>{13, 27, 46, 59, 62, 82, 92}, 6, 
                  -261
              );
              Console.WriteLine(string.Format(
                  "TEST-0...{0}",
                  result)
              );result = runner.driver(
                  new List<int>{22, 86, -64, -20, -56, -16, 86, 42, 72, -90, 10, 42, 56, 8, 50, 24, -34, 0, -78, 64, 18, 20, -84, -22, 90, -20, 86, 26, -54, 0, 90, -48, 4, 88, 18, -64, -22, -74, 48, -36, -86, -24, 88, -64, 68, 62, 92}, 38, 
                  524
              );
              Console.WriteLine(string.Format(
                  "TEST-1...{0}",
                  result)
              );result = runner.driver(
                  new List<int>{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1}, 15, 
                  131
              );
              Console.WriteLine(string.Format(
                  "TEST-2...{0}",
                  result)
              );result = runner.driver(
                  new List<int>{55, 89, 56, 85, 26, 4, 91, 91, 3, 77, 63, 59, 76, 90, 1, 94, 44, 70, 8, 54, 3, 91, 29, 95, 28, 75, 20}, 22, 
                  -954
              );
              Console.WriteLine(string.Format(
                  "TEST-3...{0}",
                  result)
              );result = runner.driver(
                  new List<int>{-94, -84, -80, -78, -66, -62, -54, -52, -26, -8, -8, -6, 4, 4, 8, 14, 26, 58, 60, 62, 62, 76, 78, 86, 92}, 18, 
                  694
              );
              Console.WriteLine(string.Format(
                  "TEST-4...{0}",
                  result)
              );result = runner.driver(
                  new List<int>{1, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 1, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0}, 25, 
                  341
              );
              Console.WriteLine(string.Format(
                  "TEST-5...{0}",
                  result)
              );result = runner.driver(
                  new List<int>{1, 2, 7, 7, 9, 14, 23, 29, 31, 31, 35, 35, 38, 41, 44, 49, 49, 50, 51, 54, 55, 56, 57, 63, 67, 69, 73, 79, 79, 80, 86, 88, 93}, 24, 
                  -506
              );
              Console.WriteLine(string.Format(
                  "TEST-6...{0}",
                  result)
              );result = runner.driver(
                  new List<int>{78, -48, 16, 22, -16, 34, 56, -20, -62, -82, -74, -40, 20, -24, -46, 64, 66, -76, 58, -84, 96, 76, 86, -32, 46}, 12, 
                  227
              );
              Console.WriteLine(string.Format(
                  "TEST-7...{0}",
                  result)
              );result = runner.driver(
                  new List<int>{0, 0, 0, 0, 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}, 29, 
                  463
              );
              Console.WriteLine(string.Format(
                  "TEST-8...{0}",
                  result)
              );result = runner.driver(
                  new List<int>{73, 76, 25, 59, 40, 85, 90, 38, 13, 97, 93, 99, 45, 7}, 12, 
                  -697
              );
              Console.WriteLine(string.Format(
                  "TEST-9...{0}",
                  result)
              );
          }
      }
  }
  
source_py: def find_the_missing_number_1(a, n):
      (i, total) = (0, 1)
      for i in range(2, (n + 2)):
          total += i
          total -= a[(i - 2)]
      return total
source_cpp: int find_the_missing_number_1(vector<int> a, int n) {
    int i, total = 1;
    for ( i = 2;
    i <= ( n + 1 );
    i ++ ) {
      total += i;
      total -= a [ i - 2 ];
    }
    return total;
  }