P1790 小胡同学的连通图

#include<cstdio>
#include<iostream>
#include<cstring>
#include<algorithm>
#include<vector>
using namespace std;
int par[105] = { 0 };
int rank0[105] = { 0 };
int root[105] = { 0 };
 
void init(int n) {
    for (int  i = 1; i <= n; i++)
    {
        par[i] = i;
        rank0[i] = 0;
    }
}
 
int find(int x) {
    if (par[x]==x)
    {
        return x;
    }
    else
    {
        return par[x] = find(par[x]);
    }
 
}
 
void unite(int x, int y) {
    x = find(x);
    y = find(y);
 
    if (x==y)
    {
        return;
    }
 
    if (rank0[x]<rank0[y])
    {
        par[x] = y;
 
    }
    else
    {
        par[y] = x;
        if (rank0[x]==rank0[y])
        {
            rank0[x]++;
        }
    }
 
}
 
bool same(int x, int y) {
    return find(x) == find(y);
}
int main() {
    int n, m;
    cin >> n >> m;
 
    init(n);
 
    int x, y;
    for (int i = 0; i < m; i++)
    {
        cin >> x >> y;
        unite(x, y);
 
    }
 
    for (int i = 1; i <= n; i++)
    {
            root[find(i)] = 1;
        
    }
    int num=0;
    for (int i = 1; i <=n; i++)
    {
        if (root[i]==1)
        {
            num++;
        }
    }
 
    num == 1 ? cout << "Yes" << endl : cout << "No" << endl;
    return 0;
}