num_province_547.cpp

class Solution {
public:
    int findCircleNum(vector<vector<int>>& isConnected) {
        int cities = isConnected.size();
        vector<int> visited(cities);
        int provinces = 0;
        for (int i = 0; i < cities; i++) {
            if (!visited[i]) {
                dfs(isConnected, visited, cities, i);
                provinces++;
            }
        }
        return provinces;
    }

    void dfs(vector<vector<int>>& isConnected, vector<int>& visited, int cities, int i) {
        for (int j = 0; j < cities; j++) {
            // 如果城市i与城市j相连，并且j还未访问过，则以j为新节点继续递归寻找相连的城市
            if (isConnected[i][j] == 1 && !visited[j]) {
                visited[j] = 1;
                dfs(isConnected, visited, cities, j);
            }
        }
    }
};