动态规划求解树形dp没有上司的舞会(c++实现)

#include<iostream>
#include<cstring>

using namespace std;
const int N=100010;
int happy[N];
int f[N][2];
int h[N],e[N],ne[N],idx;
int n;
bool has_father[N];
void add(int a,int b){
    e[idx] = b;
    ne[idx] = h[a];
    h[a] = idx++;
}

void dfs(int u){
    f[u][1] = happy[u];
    for(int i=h[u];i!=-1;i=ne[i]){
        int j=e[i];
        dfs(j);
        f[u][0] += max(f[j][1],f[j][0]);
        f[u][1] += f[j][0];
    }
}

int main(){
    ios::sync_with_stdio(false);
    cin>>n;
    for(int i=1;i<=n;i++) cin>>happy[i];
    memset(h,-1,sizeof h);
    for(int i=0;i<n-1;i++){
        int a,b;
        cin>>a>>b;
        add(b,a);
        has_father[a] = true;
    }
    int root = 1;
    while(has_father[root]) root++;
    dfs(root);
    cout<<max(f[root][0],f[root][1]);
}