蓝桥杯 2015年 第六届 生命之树(JAVA)

蓝桥杯 2015年 第六届 生命之树(JAVA)

• 无根树转有根树

package provincial_2015B;

import java.util.ArrayList;
import java.util.Scanner;

public class Ten {
	private static int[] weight;
	private static long[] total;
	private static ArrayList<ArrayList<Integer>> graph;
	private static long ans;
	
	public static void dfs(int root, int father) {
		
		for(int i = 0; i < graph.get(root).size(); i++) {
			int cur = graph.get(root).get(i);
			if(cur==father) continue;
			dfs(cur, root);
			if(total[cur]>0)
				total[root]+=total[cur];
		}
		
		if(total[root]>ans) ans=total[root];
	}
	
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		weight = new int[n+1];
		total = new long[n+1];
		for(int i = 1; i < n+1; i++) {
			int a = scan.nextInt();
			weight[i] = a;
			total[i] = a;
		}
		graph = new ArrayList<ArrayList<Integer>>();
		for(int i = 0; i < n+1; i++)
			graph.add(new ArrayList<Integer>());
		for(int i = 0; i < n-1; i++) {
			int u = scan.nextInt();
			int v = scan.nextInt();
			graph.get(u).add(v);
			graph.get(v).add(u);
		}
		dfs(1, 0);
		System.out.println(ans);
	}
}