Submission #1203339

#	Time	Username	Problem	Language	Result	Execution time	Memory
1203339		AlgorithmWarrior	The Xana coup (BOI21_xanadu)	C++20	100 / 100	60 ms	17124 KiB

xanadu

#include <bits/stdc++.h>

using namespace std;

int const INF=1e9;
int const MAX=1e5+5;
int dp[MAX][2][2];
/// dp[nod][i][j]=nr minim de schimbari sa stingem tot subarborele
/// lui nod astfel incat nod sa aiba valoarea i si am aplicat
/// toggle sau nu pe acest nod
int aux[MAX][2][2];
int n;
vector<int>tree[MAX];
bool v[MAX];

void read(){
    cin>>n;
    int i;
    for(i=1;i<n;++i){
        int u,v;
        cin>>u>>v;
        tree[u].push_back(v);
        tree[v].push_back(u);
    }
    for(i=1;i<=n;++i)
        cin>>v[i];
}

void dfs(int nod,int tata){
    int i;
    for(i=0;i<2;++i){
        aux[nod][i][0]=0;
        aux[nod][i][1]=INF;
    }
    for(auto fiu : tree[nod])
        if(fiu!=tata){
            dfs(fiu,nod);
            for(i=0;i<2;++i){
                int aux0=min(aux[nod][i][0]+dp[fiu][i][0],aux[nod][i][1]+dp[fiu][i][1]);
                int aux1=min(aux[nod][i][0]+dp[fiu][i][1],aux[nod][i][1]+dp[fiu][i][0]);
                aux[nod][i][0]=min(INF,aux0);
                aux[nod][i][1]=min(INF,aux1);
            }
        }
    dp[nod][v[nod]][0]=aux[nod][0][0];
    dp[nod][v[nod]][1]=aux[nod][1][1]+1;
    dp[nod][!v[nod]][0]=aux[nod][0][1];
    dp[nod][!v[nod]][1]=aux[nod][1][0]+1;
}

void write(int ans){
    if(ans<INF)
        cout<<ans;
    else
        cout<<"impossible";
}

int main()
{
    read();
    dfs(1,0);
    write(min(dp[1][0][0],dp[1][0][1]));
    return 0;
}

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