find_players_with_zero_or_one_losses.py

# 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.

class Solution:
    def findWinners(self, matches: List[List[int]]) -> List[List[int]]:
        countLosers = dict()
        setAllWinners = set()
        neverLost = []
        lostOnce = []
        
        for i in range(len(matches)):
            winner = matches[i][0]
            loser = matches[i][1]
            
            setAllWinners.add(winner)
            if loser not in countLosers:
                countLosers[loser] = 1
            else:
                countLosers[loser] += 1
        
        for winner in setAllWinners:
            if winner not in countLosers:
                neverLost.append(winner)
        
        for loser, lost in countLosers.items():
            if lost == 1:
                lostOnce.append(loser)
        
        neverLost.sort()
        lostOnce.sort()
        
        answer = []
        answer.append(neverLost)
        answer.append(lostOnce)
        
        return answer