LeetCode/cs/number-of-provinces.cs

public class Solution {
    private void BFS(int[][] graph, List<bool> visited, int u0) {
        var q = new Queue<int>();
        q.Enqueue(u0);
        visited[u0] = true;

        while (q.Count > 0) {
            var u = q.Dequeue();
            for (var v = 0; v < graph.Length; ++v) {
                if (graph[u][v] == 0 || visited[v]) {
                    continue;
                }

                q.Enqueue(v);
                visited[v] = true;
            }
        }
    }

    public int FindCircleNum(int[][] isConnected) {
        var visited = new List<bool>(Enumerable.Repeat(false, isConnected.Length));

        var count = 0;
        for (var i = 0; i < isConnected.Length; ++i) {
            if (visited[i]) {
                continue;
            }

            BFS(isConnected, visited, i);
            ++count;
        }

        return count;
    }
}