What is the time and space complexity of Ransom Note?

Time complexity: O(n + m). Space complexity: O(1).

Ransom Note

Easy

Code

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Solution Guide: Ransom Note

Approach

Build a frequency map from magazine. Traverse ransomNote and decrement counts for needed letters. If any required letter count is unavailable, return false.

Complexity Analysis

Time: O(n + m)
Space: O(1)

Pattern

Frequency Count

Why It Works

Every ransom letter must consume one matching magazine letter. Frequency tracking enforces one-to-one usage.

Updated Mar 2026