Submission #987182

#	Time	Username	Problem	Language	Result	Execution time	Memory
987182		batsukh2006	The Xana coup (BOI21_xanadu)	C++17	100 / 100	70 ms	19032 KiB

xanadu

#include<iostream>
#include<stdio.h>
#include<math.h>
#include<map>
#include<string>
#include<algorithm>
#include<vector>
#include<string.h>
#include<utility>
#include<set>
#include<cmath>
#include<queue>
#include<deque>
#include<functional>
#include<stack>
#include<limits.h>
#include<iomanip>
#include<unordered_map> 
#include<numeric>
#include<tuple>
#include<bitset>
using namespace std;
 
#define MOD 1000000007
#define int long long
#define ss second
#define ff first
#define endl '\n'
const int mxN=1e5+1;
int dp[mxN][2][2];
vector<int> v[mxN],s(mxN);
void dfs(int a, int p){
	for(auto node: v[a]){
		if(node!=p){
			dfs(node,a);
		}
	}
	for(int i=0; i<2; i++){
		for(int j=0; j<2; j++){
			int c=s[a]^(i^j);
			int cnt=v[a].size();
			if(p!=-1) cnt=cnt-1;
			int fneed=0,sneed=1e9;
			pair<int,int> need={0,1e9};
			for(auto node: v[a]){
				if(node!=p){
					fneed=min(need.ff+dp[node][0][i],need.ss+dp[node][1][i]);
					sneed=min(need.ff+dp[node][1][i],need.ss+dp[node][0][i]);
					need.ff=fneed;
					need.ss=sneed;
				}
			}
			if(c==1) dp[a][i][j]=need.ss+i;
			else dp[a][i][j]=need.ff+i;
		}
	}
}
void solve(){
	int n; cin>>n;
	for(int i=1; i<n; i++){
		int a,b; cin>>a>>b;
		v[a].push_back(b);
		v[b].push_back(a);
	}
	for(int i=1; i<=n; i++){
		cin>>s[i];
	}
	dfs(1,-1);
	int ans=min(dp[1][0][0],dp[1][1][0]);
	if(ans>=1e9) cout<<"impossible";
	else cout<<ans;
}
signed main(){
    // freopen("file.in", "r", stdin);
    // freopen("file.out", "w", stdout);
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    
    int t=1;
    // cin>>t;
    while(t--){
        solve();
        cout<<endl;
    }
    return 0;
}

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