Submission #1123137

#	Time	Username	Problem	Language	Result	Execution time	Memory
1123137		razivo	The Xana coup (BOI21_xanadu)	C++20	100 / 100	187 ms	40804 KiB

xanadu

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
long long n;
vector<vector<long long>> g(100000);
vector<long long> are(100000);
vector<vector<vector<long long>>> on(100000,vector<vector<long long>>(2,vector<long long>(2,0)));
pair<long long,long long> beo(vector<pair<long long,long long>> &u) {
    vector<pair<long long,long long>> d;
    d.reserve(u.size());
    long long sum = 0;
    for (long long i = 0; i < u.size(); ++i) {
        d.emplace_back(u[i].second-u[i].first,i);
        sum+=u[i].first;
    }
    if(d.size()>0)sort(d.begin(),d.end());
    long long be=sum,bo=2e5;
    for (long long i = 0; i < d.size(); ++i) {
        sum+=d[i].first;
        if(i%2==1) be=min(be,sum);
        else bo = min(bo,sum);
    }
    return {be,bo};
}
long long check(bool ch,bool me, bool p, vector<vector<vector<long long>>> &t) {
    vector<pair<long long,long long>> d;
    long long v = me ? 1 : 0;
    for (auto & i : t) {
        d.emplace_back(i[0][v],i[1][v]);
    }
    auto [e,o] = beo(d);
    bool a = me^p^ch;
    if(a) return o;
    else return e;
}
void dfs(long long cur, long long per) {
    vector<vector<vector<long long>>> t;
    for (long long i: g[cur]) {
        if(i==per) continue;
        dfs(i,cur);
        t.push_back(on[i]);
    }
    on[cur][0][0]=check(are[cur],false,false,t);
    on[cur][1][0]=check(are[cur],true,false,t)+1;
    on[cur][0][1]=check(are[cur],false,true,t);
    on[cur][1][1]=check(are[cur],true,true,t)+1;
}
int main() {
    cin>>n;
    for (long long i = 0; i < n-1; ++i) {
        long long x; long long y; cin>>x>>y; x--; y--;
        g[x].push_back(y);
        g[y].push_back(x);
    }
    for (long long i = 0; i < n; ++i) {
        long long a; cin>>a;
        are[i]=a;
    }
    dfs(0,-1);
    long long res = min(on[0][0][0],on[0][1][0]);
    if(res>n) {
        cout<<"impossible"<<endl;
    }else {
        cout<<res<<endl;
    }
}

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