547 省份数量

https://leetcode.cn/leetbook/read/top-interview-questions-hard/xdhfe5/

cost: 21m22s

class Solution {
public:
    int findCircleNum(vector<vector<int>>& isConnected) {
        int res = 0;
        for (int i = 0; i < isConnected.size(); i++) {
            if (!visited.count(i)) {
                res++;
                this->dfs(isConnected, i);
            }
        }
        return res;
    }

private:
    void dfs(vector<vector<int>>& isConnected, int k) {
        if (visited.count(k)) {
            return;
        }
        visited.insert(k);
        for (int i = 0; i < isConnected.size(); i++) {
            if (isConnected[k][i]) {
                this->dfs(isConnected, i);
            }
        }
    }
    unordered_set<int> visited;
};