Maximum Compatibility Score Sum LeetCode solution in JavaScript

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var maxCompatibilitySum = function (students, mentors) {
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  const m = students.length;
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  const n = students[0].length;
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  let max = 0;
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  dfs(0, (1 << m) - 1, 0);
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  return max;
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  function dfs(studentIdx, bitmask, scoreTally) {
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    if (studentIdx === m) {
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      max = Math.max(max, scoreTally);
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      return;
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    }
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    for (let mentorIdx = 0; mentorIdx < m; ++mentorIdx) {
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      if (bitmask & (1 << mentorIdx)) {
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        const matchScore = hammingDistance(
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          students[studentIdx],
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          mentors[mentorIdx]
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        );
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        const setMask = bitmask ^ (1 << mentorIdx);
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        dfs(studentIdx + 1, setMask, scoreTally + matchScore);
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      }
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    }
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    return;
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  }
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  function hammingDistance(studentsAnswers, mentorsAnswers) {
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    let matches = 0;
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    for (let j = 0; j < n; ++j) {
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      if (studentsAnswers[j] === mentorsAnswers[j]) ++matches;
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    }
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    return matches;
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  }
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};