2225. Find Players With Zero or One Losses

Problem statement

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 (Python3)

class Solution:
    def findWinners(self, matches: List[List[int]]) -> List[List[int]]:
        zeroLoss, oneLoss, moreLoss = set(), set(), set()
        for match in matches:
            winner, loser = match[0], match[1]

            if winner not in oneLoss and winner not in moreLoss:
                zeroLoss.add(winner)

            # Add or move loser.
            if loser in zeroLoss:
                zeroLoss.remove(loser)
                oneLoss.add(loser)
            elif loser in oneLoss:
                oneLoss.remove(loser)
                moreLoss.add(loser)
            elif loser in moreLoss:
                continue
            else:
                oneLoss.add(loser)
        return [sorted(list(zeroLoss)), sorted(list(oneLoss))]