# Time: O(S1 · S2) ; S2 is len(s1) and S2 is len(S2)
# Space: O(S2 · 26)

from collections import Counter

class Solution:
    def checkInclusion(self, s1: str, s2: str) -> bool:
        if len(s1) > len(s2): return False
        
        if len(s1) == len(s2):
            return Counter(s1) == Counter(s2)
        
        s1_counter = Counter(s1)
        
        target_length = len(s1)
        end = target_length - 1
        
        while end < len(s2):
            start = end - target_length + 1
            curr_substring = s2[start:end + 1]
            
            # Check if counters match for the given substring
            # indicated by start:end with a length of target_length
            if s1_counter == Counter(curr_substring):
                return True
            
            end += 1
        
        return False