2225. Find Players With Zero or One Losses 

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class Solution {
    public List<List<Integer>> findWinners(int[][] matches) {
        Map<Integer, Integer> playerToloseCountMap = new HashMap<>();

        for (int[] match : matches) {
            int winner = match[0], loser = match[1];
            if (!playerToloseCountMap.containsKey(winner)) {
                playerToloseCountMap.put(winner, 0);
            }
            playerToloseCountMap.put(loser, playerToloseCountMap.getOrDefault(loser, 0) + 1);
        }

        List<List<Integer>> resultList = new ArrayList<>();
        resultList.add(new ArrayList<>());
        resultList.add(new ArrayList<>());

        for (Map.Entry<Integer, Integer> entry : playerToloseCountMap.entrySet()) {
            int player = entry.getKey(), loseCount = entry.getValue();
            if (loseCount < 2) {
                resultList.get(loseCount).add(player);
            }
        }

        Collections.sort(resultList.get(0));
        Collections.sort(resultList.get(1));
        return resultList;
    }
}

References

2225. Find Players With Zero or One Losses