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

C++ 代码

#include<iostream>
#include<cstring>

using namespace std;

const int N = 6010;
int h[N], e[N], ne[N], idx;
int happy[N];
bool hasfather[N];
int f[N][2];

int 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; i = ne[i])
    {
        int j = e[i];
        dfs(j);

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

int main()
{
    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);
        hasfather[a] = true;
    }

    int root = 0;
    for (int i = 1; i <= n; i ++) 
        if (!hasfather[i])
        {
            root = i;
            break;
        }

    dfs(root);

    cout << max(f[root][0], f[root][1]);

    return 0;
}

算法2

(暴力枚举) $O(n^2)$

blablabla

时间复杂度

参考文献

C++ 代码

blablabla