Pku1947 Rebuilding Roads

题意是给一棵树,问最少删掉几条边.使得剩下的子树中有节点个数为m个的

设f[i][j]表示i号点所在的子树中选了j个点至少需要删去f[i][j]条边。

code：

 #include<cstdio>
 #include<iostream>
 #include<cmath>
 #include<cstring>
 #include<algorithm>
 #define maxn 155
 #define inf 1061109567
 using namespace std;
 char ch;
 int n,k,a,b,tot,ans,now[maxn],son[maxn<<],pre[maxn<<];
 int siz[maxn],deg[maxn],f[maxn][maxn],tmp[maxn];
 bool ok;
 void read(int &x){
     for (ok=,ch=getchar();!isdigit(ch);ch=getchar()) if (ch=='-') ok=;
     for (x=;isdigit(ch);x=x*+ch-'',ch=getchar());
     if (ok) x=-x;
 }
 void put(int a,int b){pre[++tot]=now[a],now[a]=tot,son[tot]=b;}
 void dfs(int u,int fa){
     f[u][]=,siz[u]=;
     for (int p=now[u],v=son[p];p;p=pre[p],v=son[p])
         if (v!=fa){
             dfs(v,u);
             memset(tmp,,sizeof(tmp));
             for (int i=;i<=siz[u];i++) tmp[i]=f[u][i]+;
             for (int i=;i<=siz[u];i++)
                 for (int j=;j<=siz[v];j++) tmp[i+j]=min(tmp[i+j],f[u][i]+f[v][j]);
             siz[u]+=siz[v];
             for (int i=;i<=siz[u];i++) f[u][i]=tmp[i];
         }
 }
 int main(){
     read(n),read(k);
     for (int i=;i<n;i++) read(a),read(b),put(a,b),put(b,a);
     memset(f,,sizeof(f));
     dfs(,);
     ans=f[][k];
     for (int i=;i<=n;i++) ans=min(ans,f[i][k]+);
     printf("%d\n",ans);
     return ;
 }