Find Players With Zero or One Losses

tothemoon
  December 1, 2024
Leetcode 
   305 Words  2 mins

【2225】Find Players With Zero or One Losses Medium

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] = [].

Constraints:

  • 1 <= matches.length <= 105
  • matches[i].length == 2
  • 1 <= winneri, loseri <= 105
  • winneri != loseri
  • All matches[i] are unique.

💡Solution

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   public List<List<Integer>> findWinners(int[][] matches) {
        Map<Integer,Integer> losers = new HashMap<>();
        Set<Integer> winners = new TreeSet<>();
        List<List<Integer>> ans = new ArrayList<>();
        for(int[] tmp : matches){
            int win = tmp[0];
            int lose = tmp[1];
            winners.add(win);
            losers.put(lose,losers.getOrDefault(lose,0)+1);
        }

        Set<Integer> loses = new TreeSet<>();
        for(Map.Entry<Integer,Integer> map : losers.entrySet()){
            int lose = map.getKey();
            winners.remove(lose);
            if(map.getValue() == 1){
                loses.add(lose);
            }
        }
        ans.add( new ArrayList<>(winners));
        ans.add( new ArrayList<>(loses));
        return ans;
    }

🔗 Refer links

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