text: #LeetCode 
  #3. Longest Substring Without Repeating Characters
  
  class Solution:
      def lengthOfLongestSubstring(self, s: str) -> int:
          max_len_counter = 0
          start_idx = 0
          substr = {}
          for curr_idx, item in enumerate(s):
              if item in substr.keys() and start_idx<=substr[item]: 
                  start_idx = substr[item] + 1
              else:
                  max_len_counter = max(max_len_counter, curr_idx - start_idx+1) #find max length every iteration 
              substr[item] = curr_idx         #add/update hashtable
          return  max_len_counter
  