leetcode 261 solution

lc-261.cpp

class Solution {
public:
    bool validTree(int n, vector<pair<int, int>>& edges) {
        vector<int> group(n + 1, -1);
        for(auto e : edges){
            int x = find(group, e.first);
            int y = find(group, e.second);
            if (x == y) return false;
            
            group[x] = y;
        }
        return edges.size() == n - 1;
    }
    int find(vector<int>& group, int i){
        if (group[i] == -1) return i;
        return find(group, group[i]);
    }
};