완주하지 못한 선수

Solution

function solution(participant, completion) {
  const participantObj = participant.reduce((acc, cur) => {
    acc[cur] = (acc[cur] || 0) + 1;
    return acc;
  }, {});

  completion.forEach((complete) => (participantObj[complete] -= 1));

  for (const person in participantObj) {
    if (participantObj[person]) return person;
  }
}

Review

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References

• Programmers - 완주하지 못한 선수