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#2924 - Find Champion II
Problem Description
There are n teams numbered from 0 to n - 1 in a tournament; each team is also a node in a DAG.
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.
Notes:
- A cycle is a series of nodes a1, a2, ..., an, an+1 such that node a1 is the same node as node an+1, the nodes a1, a2, ..., an are distinct, and there is a directed edge from the node ai to node ai+1 for every i in the range [1, n].
- A DAG is a directed graph that does not have any cycle.
Solution
/**
* @param {number} n
* @param {number[][]} edges
* @return {number}
*/
var findChampion = function(n, edges) {
const inDegree = new Array(n).fill(0);
for (const [, v] of edges) {
inDegree[v]++;
}
let champion = -1;
for (let i = 0; i < n; i++) {
if (inDegree[i] === 0) {
if (champion !== -1) return -1;
champion = i;
}
}
return champion;
};