242. Valid Anagram

Edited by Charles

Easy · Python · HashTable

Problem

Read the original problem on LeetCode.

The official page contains the problem statement, examples, and constraints.

Explanation, examples & other approaches

Core idea

Main idea: make two sets of counts of each character in s and t. Compare these two sets if they are the same. Remember the one-liner.

Original study notes follow, including intermediate snippets and earlier attempts.

1. Main idea: make two sets of counts of each character in s and t. Compare these two sets if they are the same.
2. Remember the one-liner.
3. Remember the string’s built-in method count(), s.count(char).

Study record

Field	Value
Attempts	2
Mastery	❚❚
The Latest Attempt	January 5, 2026

Python solution

class Solution:
    def isAnagram(self, s: str, t: str) -> bool:
            # set() is needed for the time complexity
        s_set = {char: s.count(char) for char in set(s)}
        t_set = {char: t.count(char) for char in set(t)}

        if s_set != t_set:
            return False

        return True

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