计算无向图连通子图的个数

#include <stdio.h>
#include <vector>

using namespace std;

const int maxn = 100010;
vector<int> G[maxn]; // 邻接表存储图

bool vis[maxn] = {false}; // 标记是否访问

void dfs(int v)
{
    vis[v] = true;
    for(int i = 0; i < G[v].size(); i++)
    {
        if(vis[G[v][i]] == false)
        {
            dfs(G[v][i]); // 如果该顶点未访问，深度遍历之
        }
    }
}

int main()
{
    int n, a, b;
    scanf("%d", &n);
    for(int i = 1; i < n; i++) // n - 1条边
    {
        scanf("%d%d", &a, &b);
        G[a].push_back(b);