Practice binary search - a bug on line 47, change the implicit type var to int, since double variable is generated by expression: var middle = start + (end - start)/2 causing index out of range error.

practiceBinarySearch.cs

using System;
using System.Collections.Generic; 

class Solution
{
    public static int[] FindDuplicates(int[] arr1, int[] arr2)
    {
      // your code goes here
      // 
      if(arr1 == null || arr1.Length == 0 || arr2 == null || arr2.Length == 0)
      {
        return new int[0]; 
      }
      
      // not empty - arr1 - short one, arr2 - longer one
      var length1 = arr1.Length; 
      var length2 = arr2.Length; 
      
      var firstOneSmall = length1 <= length2; 
      if(!firstOneSmall)
      {
        return FindDuplicates( arr2, arr1); 
      }
      
      var list = new List<int>(); 
      
      foreach(var number in arr1) // short one 
      {
        if(binarySearch(number, arr2))
        {
          list.Add(number); 
        }
      }
      
      return list.ToArray(); 
    }
  
    private static bool binarySearch(int search, int[] numbers)
    {
      var length = numbers.Length; 
      
      var start = 0; 
      var end = length - 1; 
      
      while(start <= end)
      {
        int  middle = start + (end - start)/ 2; 
        
        // assume that middle >= 0 => end > = start
        var middleValue = numbers[middle]; 
        
        var found = search == middleValue; 
        var less  = search < middleValue; 
        
        if(found)
        {
          return true; 
        }
        
       
        if(less)
        {
          end = middle - 1; 
        }
        else 
        {
          start = middle + 1; 
        }        
      }
      
      return false; 
    }

    static void Main(string[] args)
    {

    }
}

// M is close to N, 
// 1, 2, 3, 4, 6, 7
// -> 2 -> 3 -> 
// 3 6 7 8 20 
// 3 -> 
// while (index1 < length1 && index2 < length2)
// O(max(m, n))  m + n
// M >> N
// go over each number in small size array, binary search in big array