LeetCode 383: Ransom Note

Meta Data

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Difficulty: easy First Attempt: 2022-08-23

• Submissions: Wrong Answer → Accepted ×3

Approach

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Count magazine’s characters (Hash Table Template 1) and subtract what ransomNote needs; any shortfall fails. Python’s Counter(a) - Counter(b) keeps only positive counts, so an empty result means every character suffices.

My Attempts

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Attempt 1 returned bool(Counter(ransomNote) - Counter(magazine)), the exact opposite: a non-empty difference means a shortfall, so "a", "c" returned True. Using not passed.

Solution

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class Solution:
    def canConstruct(self, ransomNote: str, magazine: str) -> bool:
        return not (Counter(ransomNote) - Counter(magazine))

Complexity

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Time O(n + m), space O(k).

Mistakes to Avoid

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• A non-empty difference means a shortfall, so return not ..., not bool(...).

Interview Explanation

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I subtract magazine’s counts from ransomNote’s; Counter subtraction keeps only positives, so an empty result means everything is covered. Time O(n + m).