Submission #1239966

#	Time	Username	Problem	Language	Result	Execution time	Memory
1239966		ZeroCool	Longest Trip (IOI23_longesttrip)	C++20	85 / 100	7 ms	428 KiB

longesttrip

#include "longesttrip.h"
#include <bits/stdc++.h>

using namespace std;

#define ar array
#define all(v) v.begin(), v.end()

std::vector<int> longest_trip(int n, int d){
    vector<int> P;
    vector<int> Q;
    mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
    vector<int> ord(n);
    iota(all(ord), 0);
    shuffle(all(ord), rng);
    for(auto i: ord){
        vector<ar<int,2> > v;
        if(P.empty()){
            P.push_back(i);
            continue;
        }
        if(Q.empty()){
            Q.push_back(i);
            continue;
        }
        v.push_back({P.back(), i});
        v.push_back({Q.back(), i});
        v.push_back({P.back(), Q.back()});
        shuffle(all(v), rng);
        while(v.size()){
            auto [a, b] = v.back();
            v.pop_back();
            if(v.empty() || are_connected({a}, {b})){
                //flag = 1;
                if(b == i){
                    if(a == P.back())P.push_back(i);
                    else Q.push_back(i);
                }else{
                    while(P.size())Q.push_back(P.back()), P.pop_back();
                    P.push_back(i);
                }
                break;
            }
        }
    }
    //assert(0);
    if(P.empty() || Q.empty() || !are_connected(P, Q))return (P.size() > Q.size() ? P : Q);
//    assert(0);
    
    for(int i = 0;i < 2;i++){
        for(int j = 0;j < 2;j++){
            if(are_connected({P.back()}, {Q.front()})){
                for(auto u: Q)P.push_back(u);
                return P;
            }
            reverse(all(Q));
        }
        reverse(all(P));
    }

    int lo = -1, hi = P.size();
    while(hi - lo > 1){
        int mid = (lo + hi) / 2;
        vector<int> t;
        for(int i = 0;i <= mid;i++)t.push_back(P[i]);
        if(are_connected(t, Q))hi = mid;
        else lo = mid;
    }
    int mi = hi;
    lo = -1, hi = Q.size();
    while(hi - lo > 1){
        int mid = (lo + hi) / 2;
        vector<int> t;
        for(int i = 0;i <= mid;i++)t.push_back(Q[i]);
        if(are_connected({P[mi]}, t))hi = mid;
        else lo = mid;
    }
    int mj = hi;
    //assert(are_connected({P[mi]}, {Q[mj]}));
    vector<int> ans;
    for(int i = mi + 1;i < P.size();i++)ans.push_back(P[i]);
    for(int i = 0;i <= mi;i++)ans.push_back(P[i]);
    for(int i = mj;i < Q.size();i++)ans.push_back(Q[i]);
    for(int i = 0;i < mj;i++)ans.push_back(Q[i]);
    return ans;
}

• Subtask 0: 0 / 0
• Subtask 1: 5 / 5
• Subtask 2: 10 / 10
• Subtask 3: 25 / 25
• Subtask 4: 45 / 60