Find Champion II - Problem
There are n teams numbered from 0 to n - 1 in a tournament; each team is also a node in a DAG (Directed Acyclic Graph). You are given the integer n and a 0-indexed 2D integer array edges of length m representing the DAG, where edges[i] = [ui, vi] indicates that there is a directed edge from team ui to team vi in the graph.
A directed edge from a to b in the graph means that team a is stronger than team b and team b is weaker than team a.
Team a will be the champion of the tournament if there is no team b that is stronger than team a.
Return the team that will be the champion of the tournament if there is a unique champion, otherwise, return -1.
Input & Output
Example 1 — Basic Tournament
$
Input:
n = 3, edges = [[0,1],[1,2]]
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Output:
0
💡 Note:
Team 0 beats team 1, team 1 beats team 2. Team 0 has no incoming edges, so it's the unique champion.
Example 2 — No Unique Champion
$
Input:
n = 4, edges = [[0,2],[1,3],[1,2]]
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Output:
-1
💡 Note:
Both team 0 and team 1 have no incoming edges, so there's no unique champion.
Example 3 — Single Team
$
Input:
n = 1, edges = []
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Output:
0
💡 Note:
Only one team exists with no edges, so team 0 is the champion by default.
Constraints
- 1 ≤ n ≤ 100
- 0 ≤ edges.length ≤ n * (n - 1) / 2
- edges[i].length == 2
- 0 ≤ edge[i][j] ≤ n - 1
- edges[i][0] ≠ edges[i][1]
- The input is generated such that if team a is stronger than team b, team b is not stronger than team a
- The input is generated such that if team a is stronger than team b and team b is stronger than team c, then team a is stronger than team c
Visualization
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Explanation
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