Submission #849178

#	Time	Username	Problem	Language	Result	Execution time	Memory
849178		vqpahmad	Longest Trip (IOI23_longesttrip)	C++17	15 / 100	14 ms	600 KiB

longesttrip

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

using namespace std;
#define ll long long
#define pii pair<int,int>
#define F first
#define S second
#define endl '\n'
#define pb push_back
#define sz(a) (int)a.size()
#define all(a) a.begin(),a.end()
const int mod = 1e9 + 7;
const int N = 1e6 + 15;
const ll inf = 1e18;

vector<int> longest_trip(int n, int D){
	vector<int> grp[2];
	grp[0] = {0};
	grp[1] = {1};
	vector<int> num(n);
	for (int i=0;i<n;i++)num[i] = i;
	// shuffle ? 
	for (int i=2;i<n;i++){
		int u = num[i];
		if (i==n-1){
			if (are_connected({grp[0].back()}, {u})) grp[0].pb(u);
			else if (are_connected({grp[1].back()}, {u})) grp[1].pb(u);
			else {
				reverse(all(grp[1]));
				grp[0].insert(grp[0].end(), grp[1].begin(), grp[1].end());
				grp[1] = {u};
			}
			break;
		}
		int v = num[i+1];
		if (are_connected({grp[0].back()}, {u})){
			grp[0].pb(u);
			continue;
		}
		if (are_connected({grp[1].back()}, {u})){
			// what ever
			grp[1].pb(u);
			are_connected({u}, {v}) ? grp[1].pb(v) : grp[0].pb(v);
			i++;
			continue;
		}
		if (are_connected({u}, {v})){
			// mrg grp0 and grp1
			reverse(all(grp[1]));
			grp[0].insert(grp[0].end(), grp[1].begin(), grp[1].end());
			grp[1] = {u, v};
		}
		grp[1].pb(v);
		reverse(all(grp[1]));
		grp[0].insert(grp[0].end(), grp[1].begin(), grp[1].end());
		grp[1] = {u};
	}
	bool done = 0;
	if (are_connected({grp[0].back()}, {grp[1].back()})){
		reverse(all(grp[1]));
		grp[0].insert(grp[0].end(), grp[1].begin(), grp[1].end());
		done = 1;
	}
	if (!done && are_connected({grp[0].front()}, {grp[1].back()})){
		grp[1].insert(grp[1].end(), grp[0].begin(), grp[0].end());
		swap(grp[0], grp[1]);
		done = 1;
	}
	if (!done && sz(grp[1]) > 1 && are_connected({grp[0].back()}, {grp[1].front()})){
		grp[0].insert(grp[0].end(), grp[1].begin(), grp[1].end());
		done = 1;
	}
	if (!done && sz(grp[1]) > 1 && are_connected({grp[0].front()}, {grp[1].front()})){
		reverse(all(grp[0]));
		grp[0].insert(grp[0].end(), grp[1].begin(), grp[1].end());
		done = 1;
	}
	if (done) return grp[0];
	if (!are_connected(grp[0], grp[1])) return (sz(grp[0]) >= sz(grp[1]) ? grp[0] : grp[1]);
	// binary search
	int lo=0, hi = sz(grp[0]);
	while (hi-lo>1){
		int mi = (lo+hi)/2;
		vector<int> tm;
		for (int i=lo;i<mi;i++){
			tm.pb(grp[0][i]);
		}
		if (are_connected(tm, grp[1])){
			lo = mi;
		}
		else {
			hi = mi;
		}
	}
	int ans1 = lo;
	lo=0, hi = sz(grp[1]);
	while (hi-lo>1){
		int mi = (lo+hi)/2;
		vector<int> tm;
		for (int i=lo;i<mi;i++){
			tm.pb(grp[1][i]);
		}
		if (are_connected(tm, {ans1})){
			lo = mi;
		}
		else {
			hi = mi;
		}
	}
	int ans2=lo;
	vector<int> ans;
	for (int i=0;i<sz(grp[0]);i++){
		int p = (ans1+i+1)%sz(grp[0]);
		ans.pb(grp[0][p]);
	}
	for (int i=0;i<sz(grp[1]);i++){
		int p = (ans2+i)%sz(grp[1]);
		ans.pb(grp[1][p]);
	}
	return ans;
}

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