CF1092F Tree with Maximum Cost

Jennie

这也就是个裸的一批的换根dp

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
#include<queue>
#include<stack>
#include<map>
#define int long long
using namespace std;
int n;
int a[200005];
int x,y;
int head[200005];
struct e{
	int to;
	int ne;
}ed[400005];
int p;
int f[200005];
void add(int f,int to){
	ed[++p].to=to;
	ed[p].ne=head[f];
	head[f]=p;
}
int sum[200005];
void dfs(int no,int ff,int de){
	f[1]+=(de*a[no]);
	for(int i=head[no];i;i=ed[i].ne){
		int v=ed[i].to;
		if(v==ff) continue;
		dfs(ed[i].to,no,de+1);
		sum[no]+=sum[v];
	}
	sum[no]+=a[no];
}
void df(int no,int ff){
	for(int i=head[no];i;i=ed[i].ne){
		int v=ed[i].to;
		if(v==ff) continue;
		f[v]=f[no]+sum[1]-sum[v]-sum[v];
		df(v,no);
	}
	return ;
}
int ans;
signed main(){
	scanf("%lld",&n);
	for(int i=1;i<=n;++i){
		scanf("%lld",&a[i]);
	}
	for(int i=1;i<n;++i){
		scanf("%lld%lld",&x,&y);
		add(x,y);
		add(y,x);
	}
	dfs(1,1,0);
//	cout<<f[1]<<endl;
	df(1,1);
	for(int i=1;i<=n;++i){
		ans=max(ans,f[i]);
	}
	cout<<ans;
	return 0;
}