How should I practice Count Determinable Player Rankings?

Start by reading the full statement, solve the visible examples, then compare the pattern against related Google onsite interview problems in FastPrep.

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Count Determinable Player Rankings

Google● MediumINTERNONSITE INTERVIEW

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Problem statement

There are n players labeled from 0 through n - 1. Each row wins[i] = [winner, loser] records that winner defeated loser.

Results are transitive: if player A defeated player B, and player B defeated player C, then A ranks above C.

A player's strict rank is determinable when, for every other player, exactly one of these facts is inferable:

The player ranks above the other player.
The other player ranks above the player.

If both directions are reachable because of a contradictory cycle, that pair does not establish a strict ordering. Return the number of players whose strict rank is determinable.

Function

countDeterminablePlayers(n: int, wins: int[][]) → int

Examples

Example 1

n = 3wins = [[0,1],[1,2]]return = 3

Transitivity establishes 0 > 1 > 2, so every player's relation to both others is known in exactly one direction.

Example 2

n = 4wins = [[0,1],[0,2],[1,3],[2,3]]return = 2

Player 0 is above everyone and player 3 is below everyone. Players 1 and 2 are incomparable.

Example 3

n = 3wins = [[0,1]]return = 0

Every player has at least one unknown relation involving player 2.

Example 4

n = 3wins = [[0,1],[1,0],[1,2]]return = 1

Players 0 and 1 form a contradictory cycle, so neither has a strict rank. Player 2 is below both and is determinable.

Constraints

1 <= n <= 300.
0 <= wins.length <= n * (n - 1).
Every row in wins contains two valid, distinct player indices.
The same directed result may appear more than once and has the same effect as one occurrence.
Contradictory cycles may occur.