Submission #970377

#	Time	Username	Problem	Language	Result	Execution time	Memory
970377		NotLinux	The Xana coup (BOI21_xanadu)	C++17	100 / 100	74 ms	25428 KiB

xanadu

//author : FatihCihan
#include <bits/stdc++.h>
using namespace std;
#define int long long
#define all(v) v.begin() , v.end()
#define sz(a) (int)a.size()
const int N = 1e5 + 7;
const int inf = 1e9 + 7;
int n , dp[N][4] , value[N];
vector < int > tree[N];
bool is_leaf(int node){
	if(node == 1 and sz(tree[node]) == 0)return 1;
	else if(sz(tree[node]) == 1)return 1;
	else return 0;
}
void dfs(int node , int par){
	for(auto itr : tree[node]){
		if(itr != par){
			dfs(itr , node);
		}
	}
	dp[node][0] = dp[node][1] = dp[node][2] = dp[node][3] = inf;
	// dp[node][0]
	{
		vector < int > v;
		int sum = 0;
		for(auto itr : tree[node]){
			if(itr != par){
				v.push_back(dp[itr][3] - dp[itr][0]);
				sum += dp[itr][0];
			}
		}
		sort(all(v));
		v.insert(v.begin() , 0);
		for(int x = value[node];x < sz(v);x+=2){
			if(x > 0)sum += v[x-1];
			sum += v[x];
			dp[node][0] = min(dp[node][0] , sum + x);
		}
	}
	// dp[node][1]
	{
		vector < int > v;
		int sum = 0;
		for(auto itr : tree[node]){
			if(itr != par){
				v.push_back(dp[itr][3] - dp[itr][0]);
				sum += dp[itr][0];
			}
		}
		sort(all(v));
		v.insert(v.begin() , 0);
		for(int x = 1 - value[node];x < sz(v);x+=2){
			if(x > 0)sum += v[x-1];
			sum += v[x];
			dp[node][1] = min(dp[node][1] , sum + x);
		}
	}
	// dp[node][2]
	{
		vector < int > v;
		int sum = 0;
		for(auto itr : tree[node]){
			if(itr != par){
				v.push_back(dp[itr][2] - dp[itr][1]);
				sum += dp[itr][1];
			}
		}
		sort(all(v));
		v.insert(v.begin() , 0);
		for(int x = value[node];x < sz(v);x+=2){
			if(x > 0)sum += v[x-1];
			sum += v[x];
			dp[node][2] = min(dp[node][2] , sum + x);
		}
	}
	// dp[node][3]
	{
		vector < int > v;
		int sum = 0;
		for(auto itr : tree[node]){
			if(itr != par){
				v.push_back(dp[itr][2] - dp[itr][1]);
				sum += dp[itr][1];
			}
		}
		sort(all(v));
		v.insert(v.begin() , 0);
		for(int x = 1 - value[node];x < sz(v);x+=2){
			if(x > 0)sum += v[x-1];
			sum += v[x];
			dp[node][3] = min(dp[node][3] , sum + x);
		}
	}
	if(sz(tree[node]) == 1 and node != 1){
		dp[node][0] = min(dp[node][0] , dp[node][2]);
		dp[node][2] = dp[node][0];

		dp[node][1] = min(dp[node][1] , dp[node][3]);
		dp[node][3] = dp[node][1];
	}
	// cout << node << " : " << dp[node][0] << " " << dp[node][1] << " " << dp[node][2] << " " << dp[node][3] << endl;
}	
void solve(){
	cin >> n;
	for(int i = 1;i<n;i++){
		int a,b;
		cin >> a >> b;
		tree[a].push_back(b);
		tree[b].push_back(a);
	}
	for(int i = 1;i<=n;i++){
		cin >> value[i];
	}
	dfs(1,0);
	int ans = min(dp[1][0] , dp[1][3] + 1);
	if(ans >= inf)cout << "impossible" << '\n';
	else cout << ans << '\n';
}
signed main(){
	ios_base::sync_with_stdio(0);cin.tie(0);
	int testcase = 1;//cin >> testcase;
	while(testcase--)solve();
	cerr << 1000.0 * clock() / CLOCKS_PER_SEC << " ms" << endl;
}

• Subtask 1: 5 / 5
• Subtask 2: 15 / 15
• Subtask 3: 10 / 10
• Subtask 4: 40 / 40
• Subtask 5: 30 / 30