One string is an anagram of another if the second is simply a rearrangement of the first

For example, 'heart' and 'earth' are anagrams, 'python' and 'typhon' are anagrams

def anagram(s1,s2):
    """Check if s1 is a anagram of s2
    
    Args:
        s1 (str), a string consisted of 26 letters
        s2 (str), a string consisted of 26 letters
        
    Return:
        boolean
    """
    if len(s1) != len(s2): # O(1)
        return False
    
    s1 = s1.lower() # O(n)
    s2 = s2.lower() # O(n)
    
    array_1 = [0]*26 # O(n), save 26 letters in s1
    array_2 = [0]*26 # O(n), save 26 letters in s2
    
    for letter in s1: # O(n)
        index = ord(letter) - ord('a')
        array_1[index] += 1
        
    for letter in s2: # O(n)
        index = ord(letter) - ord('a')
        array_2[index] += 1
        
    for i in range(26): # O(1)
        if array_1[i] != array_2[i]:
            return False
        
    return True
            

s1 = 'heart'
s2 = 'earth'
anagram(s1, s2) # True

s1 = 'python'
s2 = 'typhon'
anagram(s1, s2) # True
            

Problem Solving with Algorithms and Data Structures using Python