pku1947rebuilding roads 树形DP

突然感觉自己代码写的好丑= =今天突然手不听话了疯狂打错字= =

显然树形DP，表示fi，j是在第i个点，有j个点连着的最小值

显然看每一棵子树的转移，显然背包

Problem: 1947		User: BPM136
Memory: 816K		Time: 0MS
Language: G++		Result: Accepted

#include<iostream>
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#include<cmath>
#include<utility>
#include<map>
#include<queue>
#include<bitset>
#define LL long long
#define fo(i,a,b) for(int i=a;i<=b;i++)
#define fd(i,a,b) for(int i=a;i>=b;i--)
#define efo(i,x) for(int i=last[x];i!=0;i=e[i].next)
using namespace std;
inline LL read()
{
	LL d=0,f=1;char s=getchar();
	while(s<'0'||s>'9'){if(s=='-')f=-1;s=getchar();}
	while(s>='0'&&s<='9'){d=d*10+s-'0';s=getchar();}
	return d*f;
}
#define N 155
#define inf 100000
int f[N][N];
int n,m;
int fa[N];
struct edge
{
	int y,next;
}e[N*N];
int last[N],ne=0;
int root=0;

void add(int x,int y)
{
	e[++ne].y=y;e[ne].next=last[x];last[x]=ne;
}

int temp[N];
void dfs(int x)
{
//	fo(i,1,siz[x])f[x][i]=1;
	fo(i,0,m)f[x][i]=inf;f[x][1]=0;
	efo(i,x)
	{
		dfs(e[i].y);
		fd(k,m,1)
		{
			int tot=f[x][k]+1;
			fo(j,1,k-1)
			tot=min(tot,f[x][j]+f[e[i].y][k-j]);
			f[x][k]=tot;
		}
	}
//	f[x][0]=0;
//	fo(i,1,siz[x])f[x][i]++;
//	cout<<x<<' '<<siz[x]<<' '<<f[x][1]<<' '<<f[x][2]<<' '<<f[x][3]<<endl;
}
/*
void predfs(int x)
{
	siz[x]=1;
	efo(i,x)
	{
		predfs(e[i].y);
		siz[x]+=siz[e[i].y];
	}
}
*/		

int main()
{
	while(scanf("%d%d",&n,&m)!=EOF)
	{
		memset(f,0,sizeof(f));
		memset(fa,0,sizeof(fa));
		ne=0;memset(last,0,sizeof(last));
		fo(i,1,n-1)
		{
			int x,y;scanf("%d%d",&x,&y);
			add(x,y);
			fa[y]=x;
		}
		fo(i,1,n)
		if(fa[i]==0)
		{
			root=i;
			break;
		}
//		predfs(root);
		dfs(root);
		int ans=f[root][m];
		fo(i,1,n)
		if(i!=root)
		ans=min(ans,f[i][m]+1);
		cout<<ans<<endl;
	}
	return 0;
}