Slide window - string search - 30 minutes performance - a few of bugs

PracticeSlideWindow_30minutesPerformance.cs

using System;
///
/// line scan 
//  brute force, O(n^2), any substring, find something
//  I cannot hear you
//  optimal 
// start, end = 0 -> scan the array 
// end-> move, include all chars, find one
// design scheme to move left point -> 
// x, y, z ->  xyxx, this way, you can move left point to next one, first x 
// yxxz -> all x, y, z are included, so I record length = 4
// yxxzy-> move left, remove y, check x, remove x, xzy => compared to existing length, min = 3, beat 3, stop
// xzy
// record count of x, y, z, this way, if I can move left point or not <- good design <- slide window 
// only scan array once -> O(n), sliding windows -> dictionary <char, int> , add/min, avoid scan the window extra 
// cannot hear you ...What is your question
// cannot hear you again
// edge case -> unique array, should not empty, alphabeat, maximum 26, 
// 
class PracticeSlideWindow {
   static void Main(string[] args) {
      Console.WriteLine("Practice Slide Window");
   }
   
   /// linear scan the array, keep two pointers, left/ right, sliding window, keep the slide window count of unqiure chars
   //  record minimum string, later just get the length 
   public static string FindSmallestSubstringContainingUniqueChars_LinearScan(string s, string unique)
   {
      if(unique == null || unique.Length == 0)   return string.Empty; 
      
      // slide winodow
      int length = s.Length; 
      
      var bookKeeping = new Dictionary<char, int>(); 
      
      // 
      bool[] uniqueAlphbetic = new bool[26]; // ? 
      
      int minimumLength = int32.Maxvalue;
      
      string mimumumStr = string.empty; 
      
      int left = 0; 
      int right = 0; 
      for(int i = 0; i < length; i++)
      {
         char current = s[i]; 
         if(!bookKeeping.ContainsKey(current)) // x
         {
            end++; // end = i
            bookKeeping.Add(current, 1);             
            
            // need to check if the string has everything
            if(slidewindowContainsAllKey(bookKeeping, unique))
            {
               int currentLength = end - start; 
               
               if(minimumLegnth > currentLength)
               {
                  minimumLength = currentLength; 
                  mimimumStr = s.substring(start, end - start); 
                  
                  // reset start, end two pointers
                  start = i; 
                  end = i; 
               }
               
               //determine if I need to move left side point
               // left or not ?
            }
         }
         else{
            // check if the left point is the same char, move left pointer
            char leftC = s[left]; 
            if(leftC == current){
               start ++; 
            }
            else 
            {
               bookKeep[current]++;  
            }
            
            // otherwsie, I need to add the count of char 
            
         }
         
      }
      
      return minimumStr; 
      
   }
}