【Luogu】P3047附近的牛（树形DP）

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cctype>
#include<cstdlib>
#define maxn 150020
#define maxk 22
using namespace std;
inline long long read(){
    long long num=0,f=1;
    char ch=getchar();
    while(!isdigit(ch)){
        if(ch==‘-‘)    f=-1;
        ch=getchar();
    }
    while(isdigit(ch)){
        num=num*10+ch-‘0‘;
        ch=getchar();
    }
    return num*f;
}

struct Edge{
    int next,to;
}edge[maxn*2];
int head[maxn],num;
inline void add(int from,int to){
    edge[++num]=(Edge){head[from],to};
    head[from]=num;
}

long long f[maxn][maxk];
long long d[maxn];

int main(){
    int n=read(),m=read();
    for(int i=1;i<n;++i){
        int x=read(),y=read();
        add(x,y);
        add(y,x);
        d[x]++;    d[y]++;
    }
    for(int i=1;i<=n;++i)    f[i][0]=read();
    for(int i=1;i<=n;++i){
        f[i][1]+=f[i][0];
        for(int j=head[i];j;j=edge[j].next){
            int to=edge[j].to;
            f[i][1]+=f[to][0];
        }
    }
    for(int j=2;j<=m;++j)
        for(int i=1;i<=n;++i){
            for(int k=head[i];k;k=edge[k].next){
                int to=edge[k].to;
                f[i][j]+=f[to][j-1];
            }
            f[i][j]-=f[i][j-2]*(d[i]-1);
        }
    for(int i=1;i<=n;++i)    printf("%lld\n",f[i][m]);
    return 0;
}