题意

最大点权独立集

思路

树形dp维护每个点取or 不取的状态

WA的点

转移方程错误：

u不取，子结点可以取或者不取，导致wa了2发。

题目链接

//#pragma GCC optimize(2)
//#pragma GCC target ("sse4")
#include<bits/stdc++.h>
//typedef long long ll;
#define ull       unsigned long long
#define int       long long
#define F           first
#define S           second
#define endl        "\n"//<<flush
#define eps         1e-6
#define base        131
#define lowbit(x)   (x&(-x))
#define db          double
#define PI          acos(-1.0)
#define inf         0x3f3f3f3f
#define MAXN        0x7fffffff
#define INF         0x3f3f3f3f3f3f3f3f
#define ferma(a,b)  pow(a,b-2)
#define mod(x)      (x%mod+mod)%mod
#define pb          push_back
#define decimal(x)  cout << fixed << setprecision(x);
#define all(x)      x.begin(),x.end()
#define rall(x)      x.rbegin(),x.rend()
#define memset(a,b) memset(a,b,sizeof(a));
#define IOS         ios::sync_with_stdio(false),cin.tie(0),cout.tie(0);
using namespace std;
#ifndef ONLINE_JUDGE
#include "local.h"
#endif
template<typename T> inline T fetch(){T ret;cin >> ret;return ret;}
template<typename T> inline vector<T> fetch_vec(int sz){vector<T> ret(sz);for(auto& it: ret)cin >> it;return ret;}
template<typename T> inline void makeUnique(vector<T>& v){sort(v.begin(), v.end());v.erase(unique(v.begin(), v.end()), v.end());}
void file()
{
#ifdef ONLINE_JUDGE
#else
    freopen("D:/LSNU/codeforces/duipai/data.txt","r",stdin);
    //  freopen("D:/LSNU/codeforces/duipai/WA.txt","w",stdout);
#endif
}
const int N=6e3+5;
struct node
{
    int v,next;
}s[N<<1];
int head[N],cnt=0,h[N],dp[N][2];
void add(int u,int v)
{
    s[++cnt].next=head[u];
    s[cnt].v=v;
    head[u]=cnt;
}
void dfs(int u,int fat)
{
    dp[u][1]=h[u];
    for(int i=head[u];i;i=s[i].next)
    {
        int v=s[i].v;
        if(v==fat)
            continue;
        dfs(v,u);
        dp[u][0]+=max(dp[v][1],dp[v][0]);
        dp[u][1]+=dp[v][0];
    }
}
signed main()
{
    IOS;
    file();
    int n;
    cin>>n;
    for(int i=1;i<=n;i++)
        cin>>h[i];
    for(int i=0;i<n;i++)
    {
        int u,v;
        cin>>u>>v;
        if(u)
            add(u,v),add(v,u);
    }
    dfs(1,0);
    cout<<max(dp[1][0],dp[1][1])<<endl;


    return 0;
}