제출 #1028446

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
1028446		mareksb	The Xana coup (BOI21_xanadu)	C++14	100 / 100	38 ms	13508 KiB

xanadu

#include <bits/stdc++.h>

using namespace std;

const int N = 1e5+5;

int dp[N][2][2];//(node,node color,toggle or no)
vector<int> mas[N];
bool color[N];

void setdp(int v,bool toggle){
    dp[v][color[v]^toggle][toggle]=toggle;
    //impossible
    dp[v][color[v]^toggle][!toggle]=N;
}
void updatedp(int v,int u, bool toggle){
    int b=dp[v][0][toggle];
    int w=dp[v][1][toggle];
    dp[v][0][toggle]=min(b+dp[u][toggle][0],w+dp[u][toggle][1]);
    dp[v][1][toggle]=min(b+dp[u][toggle][1],w+dp[u][toggle][0]);

}
void dfs(int v, int p){
    setdp(v,1);
    setdp(v,0);
    for(auto u:mas[v]){
        if(u==p)continue;
        dfs(u,v);
        updatedp(v,u,0);
        updatedp(v,u,1);
    }
}

int main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
    int n;
    cin>>n;
    for(int i=0;i<n-1;i++){
        int x,y;
        cin>>x>>y;
        mas[x].push_back(y);
        mas[y].push_back(x);
    }
    for(int i=1;i<=n;i++){
        cin>>color[i];
    }
    dfs(1,1);
    int ans=min(dp[1][0][0],dp[1][0][1]);
    if(ans>n){
        cout<<"impossible";
        return 0;
    }
    cout<<ans<<'\n';
}

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