383. Ransom Note

Return true if ransomNote can be built from the letters of magazine, using each magazine letter at most once.

Count the magazine's letters once, then spend one count per note letter. A count going below zero means we ran out.

1function canConstruct(ransomNote: string, magazine: string): boolean {
2  const count = new Map<string, number>();
3  for (const c of magazine) count.set(c, (count.get(c) ?? 0) + 1);
4  for (const c of ransomNote) {
5    const left = (count.get(c) ?? 0) - 1;
6    if (left < 0) return false;
7    count.set(c, left);
8  }
9  return true;
10}

ransomNote

magazine counts

Count the 4 magazine letters.

1 / 0

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