30分 DFS求救。。

	#include <cstdio>
#include <cstring>
#include <cmath>
#include <iostream>
#include <cmath>
using namespace std;
const int _ = 610;
int S[_];
struct Edge{
    int node;
    int nxt;
}G[_];
int head[_];
int tot = 0;
inline void add(int u, int v)
{
    G[++tot].nxt = head[u];
    G[tot].node  = v;
    head[u]      = tot;

    G[++tot].nxt = head[v];
    G[tot].node  = u;
    head[v]      = tot;
}
int n;
bool vis[_];
int dfs1(int nowNode)
{
    if(vis[nowNode]) return 0;
    vis[nowNode] = true;
    // printf("at Node:%d\n", nowNode);
    int Sum = 1;
    for(register int i = head[nowNode];i;i = G[i].nxt)
        Sum += dfs1(G[i].node);
    return S[nowNode] = Sum;
}
int Sum = 0;
int Max = 0;
void dfs2(int nowNode, int father)
{
    // printf("Node at %d \n", nowNode);
    if(!G[head[nowNode]].nxt)
    {
        // cout<< Sum<<endl;
        Max = max(Max, Sum);
        return ;
    }
    for(register int i = head[nowNode];i;i = G[i].nxt)
    {
        if(G[i].node == father) continue;
        Sum += S[ G[i].node ];
        // printf("Give up node %d\n", G[i].node);
        for(register int j = head[nowNode];j;j = G[j].nxt)
        {
            if(i == j || G[j].node == father)continue;
            dfs2(G[j].node, nowNode);
        }
        Sum -= S[ G[i].node ];
    }
}
int main()
{
    int m;
    scanf("%d%d", &n, &m);
    
    for(register int i = 1;i <= m;i++)
    {
        int tx, ty;
        scanf("%d%d", &tx, &ty);
        add(tx, ty);
    }
    memset(vis, false, sizeof(vis));
    dfs1(1);
    // for(register int i = 1;i <= n;i++)
    // {
        // printf("node %d have %d sons\n", i, S[i]);
    // }
    dfs2(1, -1);
    printf("%d", n - Max);
    // system("pause");
    return 0;
}
/*
7 6
1 2
1 3
2 4
2 5
3 6
3 7
*/