[算法][哈希表][排序] [leetcode]2225. 找出输掉零场或一场比赛的玩家

题目地址

https://leetcode.cn/problems/find-players-with-zero-or-one-losses/description/

题目描述

代码及思路

class Solution {
    
    
    public List<List<Integer>> findWinners(int[][] matches) {
    
    
        //创建一个map记录比赛胜者组
        //创建一个map记录比赛败者组
        //全胜者不应该出现在败者组中
        //恰好只输了一场的在败者组中失败次数为1
        Map<Integer, Integer> winnerMap = new HashMap();
        Map<Integer, Integer> loserMap = new HashMap();
        for (int[] m : matches) {
    
    
            if (winnerMap.containsKey(m[0])) {
    
    
                winnerMap.put(m[0], winnerMap.get(m[0])+1);
            } else {
    
    
                winnerMap.put(m[0], 1);
            }

            if (loserMap.containsKey(m[1])) {
    
    
                loserMap.put(m[1], loserMap.get(m[1] )+1);
            } else {
    
    
                loserMap.put(m[1], 1);
            }
        }

        List<Integer> answers0List = winnerMap.keySet().stream().filter(e -> !loserMap.containsKey(e)).sorted().collect(Collectors.toList());
        List<Integer> answer1List = loserMap.entrySet().stream().filter(e->e.getValue()==1).map(e->e.getKey()).sorted().collect(Collectors.toList());

        List<List<Integer>> ans = new ArrayList<>();
        ans.add(answers0List);
        ans.add(answer1List);
        return ans;
    }
}