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Valid Anagram

easy
Blind 75NeetCode 150stringshashing

Problem

Given two strings, determine whether one is a rearrangement of the other. Two strings are anagrams when they contain exactly the same characters with the same frequencies.

Examples

Input: s = "anagram", t = "nagaram"
Output: true
Both strings use the same letters the same number of times.
Input: s = "rat", t = "car"
Output: false
The letter sets differ.

Constraints

  • • 1 <= s.length, t.length <= 5 * 10^4
  • • Strings consist of lowercase English letters
Hints(tap to reveal)
  • 1. If the lengths differ they cannot be anagrams.
  • 2. Count how many times each character appears.
Optimal approach(spoiler)
  1. If the two lengths differ, return false right away.
  2. Build a frequency count of characters in the first string.
  3. Decrement that count for each character in the second string.
  4. If any count goes negative or is non-zero at the end, return false.
  5. O(n) time, O(1) space for a fixed alphabet.

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