6:41 PM mock interview with Bryant - June 20, 2020 - binary search algorithm

Binary search

6:41

Array - find the largest number

Sorted in ascending order - O(1) access - 
binary search given a number logn
Not sorted - go over each element O(N) - max 


// [1, 2, 2] - return 1 or 2, duplicate 
Int  FindGivenNumber(int[] numbers, int search)  // [1, 2], 2
{
	if(numbers == null || numbers.Length == 0)  // ok
	Return -1; 

           // ascending order
 Var length = numbers.Length; // 2
 Var start =0; //
 Var end = length - 1; // 1

 if(search < numbers[start] || search> numbers[end])  // 2 < 1 || 2 > 2 -> false
Return -1; 
// start <= end 
while(numbers[start] <=  numbers[end]) // start = end = 1, true
{
    var middle = start + (end - start)/ 2; // 1 = 1 + (1-1)/2 = 1
    var middleValue = numbers[middle];// numbers[1] = 2

    if(middleValue == search) // 2 == 2 true
return middle; // 1

    if(middleValue < search) // 1 < 2 true
      start = middle + 1; // remove left half - start = 1
    else   
      end = middle - 1; // remove right half
}

return -1; 
}




//recursive

Int  FindGivenNumber(int[] numbers, int start, int end, int search)  // [1, 2], 2
{
	if(numbers == null || numbers.Length == 0 || start > end)  // 
	Return -1; 

           // ascending order
 Var length = numbers.Length; // 2

 if(search < numbers[start] || search> numbers[end])  
Return -1; 

var middle = start + (end - start)/ 2; 
var middleValue = numbers[middle];

 if(middleValue == search) // 
return middle; // 

if(search > middleValue ) // 
{   start = middle +1; 
}
else 
{
     end = middle - 1; 
}

 return FindGivenNumber( numbers, start, end, search) 

}




what went well
Simple question to find element in the sorted array - answer is simple and correct
Sorted array - binary search, write code and tested and it works

What would you do differently?
As interviewer gave me hint, I should ask if duplicate value in sorted array, then it may be leftmost one or last one or doesn not  matter
Testing - learn how to unit test
First, pick [1, 2] compared to [1,2,3,4]
Good enough, I need to do step by step to show - do not skip anything 
Mix so many things, index value with array number, and then a few places as well. 
Preparation of interview - get google docs ready - prepare technical for mock interview 
Zoom - time limit
Facebook messenger
Skype - 
Continue to use it
Headphone - turn off your phone ring - wechat rings - polite

Should ask interviewer:
all numbers in the memoary
Sorted array, what if the number has duplicate 
and more 

Search - better to name as target
Turn off mobile phone
Save Google docs link to prepare for mock interview
Do not cut the interviewer when we talk
interviewer suggested me to use test case [1, 2], I chose [1, 2, 3, 4]

Remove redundant code
assume that numbers are valid - I still wrote a line to check if the number is valid 

Prepare better for interview:
Kill all browser windows on my computer, stop stock research ;