Find Players With Zero or One Losses

export function findWinners(matches: number[][]): number[][] {
  const players = new Set<number>();
  const lostCounts = new Map<number, number>();
 
  for (const [winner, loser] of matches) {
    players.add(winner);
    players.add(loser);
    lostCounts.set(loser, (lostCounts.get(loser) || 0) + 1);
  }
 
  const notLostAnyMatches: number[] = [];
  const lostOneMatch: number[] = [];
  for (const player of players) {
    const lostCount = lostCounts.get(player) || 0;
    if (1 < lostCount) {
      continue;
    }
    if (lostCount === 0) {
      notLostAnyMatches.push(player);
    } else {
      lostOneMatch.push(player);
    }
  }
 
  notLostAnyMatches.sort((a, b) => a - b);
  lostOneMatch.sort((a, b) => a - b);
 
  return [notLostAnyMatches, lostOneMatch];
}