Sort algorithm customized only using one API - flip - mock practice in 30 minutes

ONxN_Sorting_usingOneAPI_mock.cs

using System;

class Solution
{
    public static int[] PancakeSort(int[] arr)
    {
      if(arr == null || arr.Length == 0)
      {
        return new int[0]; 
      }
      
      // let me flip 5 from test case [1, 5, 4, 3, 2] to the last one
      var length = arr.Length; 
      
      var countFound = 0; 
      
      
      while(countFound < length)  // 5 , 1 < 5
      {
        var maxIndex = 0; 
        var maxValue = arr[0]; // [2, 3, 4, 1, 5]
        
        
        var subArrayLength = length - countFound;  // 5, 4
        
        // iterate the subarray 
        for(int i = 1; i < subArrayLength; i++) // 
        {
          var visit = arr[i]; 
          var isBigger = visit > maxValue; 
          if(isBigger)
          {
            maxValue = visit; 
            maxIndex = i; 
          }
        }
      
        flip(arr, maxIndex + 1); // 1
        flip(arr, subArrayLength); // 5, 4
        
        countFound ++; // 1
      }
      
      return arr; 
    }

    // reverse
    private static void flip(int[] arr, int k)
    {
      if(k <= 0)
      {
        return; 
      }
      
      int start = 0; 
      int end = k - 1; 
      
      while(start < end)
      {
        var tmp = arr[start]; 
        
        arr[start] = arr[end]; 
        arr[end] = tmp; 
        
        start++; 
        end--; 
      }      
    }
  
    static void Main(string[] args)
    {

    }
}

/*
arr = [1, 5, 4, 3, 2]
flip(arr, k), first k element - reverse 
[1, 2, 3, 4, 5]
sort the array left -> right 
right -> left 
above 5 -> O(n) -> 1
flip -> 5
flip first 5 element -> last one 
O(n) + O(n - 1) + ...+ O(1) = O(n*(n+1)/2 ) time complexity 
extra array O(1)

edge: null, 0
size = 1
sample test case 

*/