2022.04.03(LC_5235_找出输掉零场或一场比赛的玩家)

 方法：设置标志位+计数

class Solution {
    public List<List<Integer>> findWinners(int[][] matches) {
        List<List<Integer>> ans = new ArrayList<>();
        boolean[] flag = new boolean[100001];
        int[] counter = new int[100001];
        for (int[] m : matches) {
            flag[m[0]] = true;
            flag[m[1]] = true;
            counter[m[1]]++;
        }
        List<Integer> zero = new ArrayList<>();
        List<Integer> one = new ArrayList<>();
        for (int i = 1; i <= 100000; i++) {
            if (flag[i]) {
                if (counter[i] == 0) {
                    zero.add(i);    
                } else if (counter[i] == 1) {
                    one.add(i);
                }
            } 
        }
        ans.add(zero);
        ans.add(one);
        return ans;
    }
}