from collections import Counter

class Solution:
  def findSubstring(self, text, pattern):
    
    counter_freq = Counter(pattern)
    text_freq = {}
    result = ""
    short_len = float('inf')
    
    # method that checks if text map contains the counter map 
    def found(text_freq, counter_freq):
      for char, freq in counter_freq.items():
        if char not in text_freq or freq > text_freq[char]:
          return False
      return True

    i = 0
    j = 0

    while i < len(text):
      # append i frequency to the text map and move i 
      text_freq[text[i]] = text_freq.get(text[i], 0)
      text_freq[text[i]] += 1
      i += 1

      # while we can find the pattern in the text
      while found(text_freq, counter_freq):
        # if we found shorter string that has the pattern
        if i - j + 1 < short_len:
          short_len = i - j + 1
          result = text[j:i]
        
        # remove j frequency from the text map and move j
        text_freq[text[j]] -= 1
        if text_freq[text[j]] == 0:
          del text_freq[text[j]]
        j += 1
   
    return result;