NOI 2002 贪吃的九头龙

树形dp

#include<bits/stdc++.h>
#define N 305
using namespace std;
struct LEB{
    int to,nxt,w;
}e[N<<];
int f[N][N][];
int tmp[N][];
int head[N];
int n,m,k,x,z,y,cnt;
void Build(int x,int y,int z){
    e[++cnt]=(LEB){y,head[x],z};
    head[x]=cnt;
}
void dp(int x,int y){
    f[x][][]=f[x][][]=;
    for (int i=head[x];i;i=e[i].nxt){
        int z=e[i].to;
        if (z==y)
            continue;
        dp(z,x);
        memcpy(tmp,f[x],sizeof(tmp));
        memset(f[x],,sizeof(f[x]));
        for (int j=;j<=k;j++)
            for(int t=;t<=j;++t){
                f[x][j][]=min(f[x][j][],min(f[z][t][]+tmp[j-t][]+(m==)*e[i].w,f[z][t][]+tmp[j-t][]));
                f[x][j][]=min(f[x][j][],min(f[z][t][]+tmp[j-t][]+e[i].w,f[z][t][]+tmp[j-t][]));
            }
    }
}
int main(){
    scanf("%d%d%d",&n,&m,&k);
    if (n-k<m-){
        printf("-1\n");
        return ;
    }
    for (int i=;i<n;i++){
        scanf("%d%d%d",&x,&y,&z);
        Build(x,y,z);
        Build(y,x,z);
    }
    memset(f,,sizeof(f));
    dp(,);
    printf("%d\n",f[][k][]);
    return ;
}