Python: Check if two given strings are isomorphic to each other or not

Last update on May 24 2025 10:49:01 (UTC/GMT +8 hours)

Isomorphic Strings Check

In abstract algebra, a group isomorphism is a function between two groups that sets up a one-to-one correspondence between the elements of the groups in a way that respects the given group operations. If there exists an isomorphism between two groups, then the groups are called isomorphic.
Two strings are isomorphic if the characters in string A can be replaced to get string B
Given "foo", "bar", return false.
Given "paper", "title", return true.
Write a Python program to check if two given strings are isomorphic to each other or not.

Sample Solution:

Python Code:

# Function to check if two strings are isomorphic
def isIsomorphic(str1, str2):          
    dict_str1 = {}  # Dictionary to store mapping for characters in str1
    dict_str2 = {}  # Dictionary to store mapping for characters in str2
    
    # Enumerate through characters in str1 and store their positions in the dictionary
    for i, value in enumerate(str1):
        dict_str1[value] = dict_str1.get(value, []) + [i]
            
    # Enumerate through characters in str2 and store their positions in the dictionary
    for j, value in enumerate(str2):
        dict_str2[value] = dict_str2.get(value, []) + [j]
    
    # Check if the values (positions) in the dictionaries are the same after sorting
    if sorted(dict_str1.values()) == sorted(dict_str2.values()):
        return True
    else:
        return False

# Test cases
print(isIsomorphic("foo", "bar"))
print(isIsomorphic("bar", "foo"))
print(isIsomorphic("paper", "title"))
print(isIsomorphic("title", "paper"))
print(isIsomorphic("apple", "orange"))
print(isIsomorphic("aa", "ab"))
print(isIsomorphic("ab", "aa"))

Sample Output:

False
False
True
True
False
False
False

Explanation:

Here is a breakdown of the above Python code:

• Define a function named "isIsomorphic()" that takes two strings (str1 and str2) as input.
• Create two dictionaries (dict_str1 and dict_str2) to store the mapping of characters to their positions in each string.
• Use "enumerate" to iterate through characters in 'str1' and 'str2', and update the dictionaries accordingly.
• Check if the values (positions) in the dictionaries are the same after sorting.
• Return 'True' if the strings are isomorphic, and 'False' otherwise.
• Test the function with various input strings and print the results.

Visual Presentation:

Flowchart:

For more Practice: Solve these Related Problems:

• Write a Python program to check if two strings are isomorphic by establishing a one-to-one character mapping.
• Write a Python program to determine if two strings are isomorphic using dictionaries to track character correspondences.
• Write a Python program to validate the isomorphism of two strings by ensuring consistent and unique character mappings.
• Write a Python program to compare two strings and return whether they are isomorphic by verifying bidirectional mappings.

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