2225. Find Players With Zero or One Losses

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# 題目敘述

You are given an integer array matches where matches[i] = [winneri, loseri] indicates that the player winneri defeated player loseri in a match.

Return a list answer of size 2 where:

• answer[0] is a list of all players that have not lost any matches.
• answer[1] is a list of all players that have lost exactly one match.

The values in the two lists should be returned in increasing order.

Note:

• You should only consider the players that have played at least one match.
• The testcases will be generated such that no two matches will have the same outcome.

# Example 1

Input: matches = [[1,3],[2,3],[3,6],[5,6],[5,7],[4,5],[4,8],[4,9],[10,4],[10,9]]
Output: [[1,2,10],[4,5,7,8]]
Explanation:
Players 1, 2, and 10 have not lost any matches.
Players 4, 5, 7, and 8 each have lost one match.
Players 3, 6, and 9 each have lost two matches.
Thus, answer[0] = [1,2,10] and answer[1] = [4,5,7,8].

# Example 2

Input: matches = [[2,3],[1,3],[5,4],[6,4]]
Output: [[1,2,5,6],[]]
Explanation:
Players 1, 2, 5, and 6 have not lost any matches.
Players 3 and 4 each have lost two matches.
Thus, answer[0] = [1,2,5,6] and answer[1] = [].

# 解題思路

# Solution

import java.util.ArrayList;

import java.util.Collections;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

class Solution {

    public List<List<Integer>> findWinners(int[][] matches) {

        List<List<Integer>> ans = new ArrayList<>();

        List<Integer> noLost = new ArrayList<>();

        List<Integer> oneLost = new ArrayList<>();

        Map<Integer, Integer> map = new HashMap<>();

        for(int[] matche : matches){

            if(!map.containsKey(matche[0])){

                map.put(matche[0], 0);

            }

            if(!map.containsKey(matche[1])){

                map.put(matche[1], 1);

            }else if(map.get(matche[1]) == 0){

                map.put(matche[1], 1);

            }else{

                map.put(matche[1], 2);

            }

        }

        for(int m : map.keySet()){

            if(map.get(m) == 0){

                noLost.add(m);

            }else if(map.get(m) == 1){

                oneLost.add(m);

            }

        }

        Collections.sort(noLost);

        Collections.sort(oneLost);

        ans.add(noLost);

        ans.add(oneLost);

        return ans;

    }

}