题目描述

blablabla

样例

blablabla

算法1

(暴力枚举) $O(n^2)$

blablabla

时间复杂度

参考文献

Java 代码

import java.util.*;
import java.io.*;

public class Main{

    static int[] happy;
    static int[] h;
    static int[] e;
    static int[] ne;
    static int idx = 0;
    static int[][] f; 
    static int N;
    static boolean[] st;
    static BufferedReader read = new BufferedReader(new InputStreamReader(System.in));
    static PrintWriter write = new PrintWriter(System.out);
    public static void main(String[] args) throws IOException{
        String[] s = read.readLine().split("\\s+");
        N = Integer.parseInt(s[0]);  
        st = new boolean[N+1];
        happy = new int[N+1];
        h = new int[N+1];
        e = new int[N+1];
        ne = new int[N+1];
        f = new int[N+1][2];
        for (int i = 1; i <= N; i++) {
            s = read.readLine().split("\\s+");
            happy[i] = Integer.parseInt(s[0]);
        }
        Arrays.fill(h, -1);
        for (int i = 1; i < N; i++) {
            s = read.readLine().split("\\s+");
            int a = Integer.parseInt(s[0]);
            int b = Integer.parseInt(s[1]);
            add(b,a);
            st[a] = true;
        }
        int root = 1;
        while(st[root]){
            root ++;

        }
        dfs(root);
        write.print(Math.max(f[root][0], f[root][1]));
        write.flush();
        write.close();
        read.close();
    }

    static 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][1] += f[j][0];
            f[u][0] += Math.max(f[j][1], f[j][0]);
        }
    }

    static void add(int a,int b)
    {
        e[idx] = b;
        ne[idx] = h[a];
        h[a] = idx ++;
    }

}