leetcode547 省份数量

题目可见：https://leetcode-cn.com/problems/number-of-provinces/
很明显是一个并查集，上模版即可：

class Solution {
public:
    int findCircleNum(vector<vector<int>>& isConnected) {
        init(isConnected.size());
        for(int i =0 ; i < isConnected.size(); i++) {
            for(int j = i+1; j < isConnected[i].size(); j++) {
                if(isConnected[i][j]) merge(i,j); 
            }
        }
        int ans = 0;
        for(int i = 0; i < isConnected.size(); i++) {
            if(p[i]==i) ans++;
        }
        return ans;
    }

private:
    int p[210];
    void init(int n){
        for(int i=0;i<n;i++) {
            p[i] = i;
        }
    }

    int find(int x) {
        if(p[x] != x) p[x] = find(p[x]);
        return p[x];
    }

    void merge(int a, int b){
        a = find(a);
        b = find(b);
        p[a] = b;
    }
};