## Facebook Interview Question

**Country:**United States

P1>P2 and P2>P3 implies P1>P3

The first question is basically finding the max in an array. First compare between P1 and P2, store the bigger one and then match the result with P3. This process goes on till PN.

The second question is basically sorting the players. This is merge sort where the results of the pairwise matches determine which element is larger.

```
// players: [0, n-1]
// w[0] wins w[1]
func Question1(n int, wins [][]int) int {
// Two iteration, but strictly O(1) space
var loser int
for _, w := range wins {
loser = w[1]
// mark loser's index using negative value
wins[loser][0] = math.MinInt32 + abs(wins[loser][0])
}
for i := 0; i < n; i++ {
// winner never loses
if wins[i][0] > 0 {
return i
}
}
return -1
}
func Question2(n int, wins [][]int) []int {
// topological sort
// O(n) time, O(n) space
games := make(map[int][]int)
ans, degrees := make([]int, n), make([]int, n)
for _, w := range wins {
games[w[1]] = append(games[w[1]], w[0])
degrees[w[0]]++
}
// there should always be all-game losers, otherwise the deadlock occurs
var queue []int
for i, in := range degrees {
if in == 0 {
queue = append(queue, i)
}
}
for len(queue) > 0 {
size := len(queue)
for i := 0; i < size; i++ {
cur := queue[i]
n--
ans[n] = queue[i]
for _, winner := range games[cur] {
degrees[winner]--
if degrees[winner] == 0 {
queue = append(queue, winner)
}
}
}
queue = queue[size:]
}
return ans
}
```

def find_tournament_winner(matches):

winner = None

for match in matches:

player1, player2 = match

if winner is None:

winner = player1

if winner == player1:

winner = player1

elif winner == player2:

winner = player2

return winner

# Example usage:

matches = [("P1", "P2"), ("P2", "P3"), ("P3", "P1"), ("P4", "P1")]

winner = find_tournament_winner(matches)

print("Winner of the tournament:", winner)

```
def find_tournament_winner(matches):
winner = None
for match in matches:
player1, player2 = match
if winner is None:
winner = player1
if winner == player1:
winner = player1
elif winner == player2:
winner = player2
return winner
# Example usage:
matches = [("P1", "P2"), ("P2", "P3"), ("P3", "P1"), ("P4", "P1")]
winner = find_tournament_winner(matches)
print("Winner of the tournament:", winner)
```

- yp November 25, 2021