Submission #1158571

#	Time	Username	Problem	Language	Result	Execution time	Memory
1158571		alexander707070	Power Plant (JOI20_power)	C++20	100 / 100	81 ms	27716 KiB

power

#include<bits/stdc++.h>
#define MAXN 200007
using namespace std;

int n,a,b,ans,dp[MAXN],cnt;

int down[MAXN],up[MAXN],sdown[MAXN],sup[MAXN];

char c[MAXN];
vector<int> v[MAXN];

void dfs(int x,int p){
	down[x]=c[x]-'0';

	int sum=0;
	for(int i:v[x]){
		if(i==p)continue;
		
		dfs(i,x);
		sum+=down[i];
	}

	sdown[x]=sum;
	down[x]=max(down[x] , sum-down[x]);
}

void dfs2(int x,int p){
	int loss=c[x]-'0';

	if(p!=0){
		sup[x]=max( (c[p]-'0') - loss , sup[p] + sdown[p] - down[x] - loss );
	}else sup[x]=-loss;

	for(int i:v[x]){
		if(i==p)continue;
		dfs2(i,x);
	}
}

int main(){

	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);

	cin>>n;
	for(int i=1;i<=n-1;i++){
		cin>>a>>b;
		v[a].push_back(b);
		v[b].push_back(a);
	}

	for(int i=1;i<=n;i++){
		cin>>c[i];
		if(c[i]=='1')cnt++;
	}

	ans=min(cnt,2);

	dfs(1,0);
	dfs2(1,0);

	for(int i=1;i<=n;i++){
		ans=max(ans, sdown[i] + sup[i]);
	}

	ans=min(ans,cnt);
	cout<<ans<<"\n";

	return 0;
}

• Subtask 1: 6 / 6
• Subtask 2: 41 / 41
• Subtask 3: 53 / 53