poj1947 Rebuilding Roads

#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstring>
using namespace std;
#define pb push_back
#define mp make_pair
#define se second
#define fs first
#define LL long long
#define CLR(x) memset(x,0,sizeof x)
#define MC(x,y) memcpy(x,y,sizeof(x))  
#define SZ(x) ((int)(x).size())
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin();it!=(c).end();it++)
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1 
//typedef pair<int,int> P;
const double eps=1e-9;
const int maxn=200;
const int mod=1e9+7;
const int INF=1e9;

int N,P,cnt;
int head[maxn],Size[maxn],num[maxn];
int dp[maxn][maxn];

struct Edge{
    int v,nxt;
}edge[maxn];

void Init(){
    cnt=0;
    memset(head,-1,sizeof(head));
    memset(Size,0,sizeof(Size));
    memset(num,0,sizeof(num));
    for(int i=0;i<=N;i++)
    for(int j=0;j<=N;j++) dp[i][j]=INF;
}

void addEdge(int u,int v){
    edge[cnt].v=v;
    edge[cnt].nxt=head[u];
    head[u]=cnt++;
    num[u]++;
}

void dfs(int u){
    Size[u]=1;
    for(int i=head[u];i!=-1;i=edge[i].nxt){
        int v=edge[i].v;
        dfs(v);
        Size[u]+=Size[v];
    }
    dp[u][Size[u]]=0;
}

void DP(int u){
    for(int i=head[u];i!=-1;i=edge[i].nxt){
        int v=edge[i].v;
        DP(v);
        for(int j=Size[u];j>0;j--)
        for(int s=1;s<=min(j,Size[v]);s++) dp[u][j]=min(dp[u][j],dp[u][j-s]+dp[v][s]-1);
    }
}

int main(){
    scanf("%d%d",&N,&P);
    Init();
    for(int i=1;i<=N-1;i++){
        int x,y;
        scanf("%d%d",&x,&y);
        addEdge(x,y);
    }
    for(int i=1;i<=N;i++) dp[i][1]=num[i];
    dfs(1);
    DP(1);
    int ans=dp[1][P];
    for(int i=2;i<=N;i++) ans=min(ans,dp[i][P]+1);
    printf("%d\n",ans);
    return 0;
}