285. 没有上司的舞会 - AcWing题库

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<string>
#include<cstring>
#include<cmath>
#include<ctime>
#include<algorithm>
#include<utility>
#include<stack>
#include<queue>
#include<vector>
#include<set>
#include<map>
using namespace std;
typedef long long LL;
const int N = 6e3 + 5;
vector<int>G[N];
int f[N][2],w[N],s[N],v[N];
int n;void dfs(int root) {f[root][1] = w[root];for (int i = 0; i < G[root].size();i++) {if (v[G[root][i]])continue;int j = G[root][i];dfs(j);f[root][0] += max(f[j][0], f[j][1]);f[root][1] += f[j][0];}
}int main() {cin >> n;for (int i = 1; i <= n; i++) {cin >> w[i];}for (int i = 1, a, b; i < n; i++) {cin >> a >> b;G[b].push_back(a);s[a] = 1;}int root = 1;while (s[root])root++;v[root] = 1;dfs(root);cout << max(f[root][0], f[root][1]) << endl;return 0;
}