树的重心

 最大子树最小的节点

#include<bits/stdc++.h>
using namespace std;
const int maxn = 1e5;
int vis[maxn],Size[maxn];

void dfs(int x)
{
    vis[x] = 1;
    Size[x] = 1;
    int max_part = 0;
    for(int i = head[x]; i !=-1; i=edge[i].next)
    {
        int to = edge[i].to;
        if(!vis[to])
            dfs(to);
        Size[x] +=Size[to];
        max_part  = max(max_part,Size[to]);
    }
    max_part = max(max_part,n-Size[x]);
    if(max_part<ans)
    {
        ans = max_part;
        pos = x;
    }

}

int main()
{
    cout << "Hello world!" << endl;
    return 0;
}