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7. Valid Anagram

easyAsked at Adyen

Given two strings, return true if one is an anagram of the other.

By Alex Chen, Founder, InterviewChamp.AI · Last verified

Problem

Given two strings s and t, return true if t is an anagram of s. An anagram uses exactly the same letters with the same counts.

Constraints

  • 1 <= s.length, t.length <= 5 * 10^4
  • s and t consist of lowercase English letters.

Examples

Example 1

Input
s = "anagram", t = "nagaram"
Output
true

Example 2

Input
s = "rat", t = "car"
Output
false

Approaches

1. Sort and compare

Sort both strings and compare.

Time
O(n log n)
Space
O(n)
return s.length === t.length && [...s].sort().join('') === [...t].sort().join('');

Tradeoff:

2. Frequency counter

Count chars in s, decrement for t, ensure every bucket ends at zero.

Time
O(n)
Space
O(1)
function isAnagram(s, t) {
  if (s.length !== t.length) return false;
  const counts = new Array(26).fill(0);
  for (let i = 0; i < s.length; i++) {
    counts[s.charCodeAt(i) - 97]++;
    counts[t.charCodeAt(i) - 97]--;
  }
  return counts.every(c => c === 0);
}

Tradeoff:

Adyen-specific tips

Adyen uses this to probe whether you reach for a fixed-size bucket array — a pattern they reuse for currency-code histograms in their fraud-signal pipeline.

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Output

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