LeetCode 2924: Find Champion II Solution

Master LeetCode problem 2924 (Find Champion II), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

2924. Find Champion II

Medium

Graph

Problem Explanation

Explanation

To solve this problem, we can build a directed graph based on the edges provided and then perform a topological sorting. After the topological sorting, we check if there is a unique champion. If there is a unique champion, we return that team number, otherwise, we return -1.

Build the directed graph from the given edges.
Perform topological sorting.
Check for a unique champion.
Return the champion if unique, else return -1.

Time complexity: O(n + m) where n is the number of teams and m is the number of edges. Space complexity: O(n + m)

Solution Code

class Solution {
    public int findChampion(int n, int[][] edges) {
        List<Integer>[] graph = new ArrayList[n];
        int[] indegree = new int[n];

        for (int i = 0; i < n; i++) {
            graph[i] = new ArrayList<>();
        }

        for (int[] edge : edges) {
            int from = edge[0];
            int to = edge[1];
            graph[from].add(to);
            indegree[to]++;
        }

        Queue<Integer> queue = new LinkedList<>();
        for (int i = 0; i < n; i++) {
            if (indegree[i] == 0) {
                queue.offer(i);
            }
        }

        int champion = -1;
        int count = 0;
        while (!queue.isEmpty()) {
            int node = queue.poll();
            champion = node;
            count++;

            for (int neighbor : graph[node]) {
                indegree[neighbor]--;
                if (indegree[neighbor] == 0) {
                    queue.offer(neighbor);
                }
            }
        }

        return count == 1 ? champion : -1;
    }
}

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