Submission #121150

#	Time	Username	Problem	Language	Result	Execution time	Memory
121150		WhipppedCream	Roller Coaster Railroad (IOI16_railroad)	C++17	34 / 100	118 ms	46968 KiB

railroad

#include "railroad.h"
#include <bits/stdc++.h>
#pragma GCC optimize ("O3")
#pragma GCC target ("sse4")
using namespace std;
#define X first
#define Y second
#define pb push_back
typedef pair<int, int> ii;
typedef long long ll;

const int maxn = 18;

ll dp[maxn][1<<maxn];

int n;

int s[maxn], t[maxn];

const int maxN = 4e5+5;

int sw[maxN];
vector<int> adj[maxN];

ll solve(int u, int bit)
{
	if(bit == (1<<n)-1) return 0;
	if(dp[u][bit] != -1) return dp[u][bit];
	ll best = 1e18;
	for(int i = 0; i< n; i++)
	{
		if(bit&(1<<i)) continue;
		best = min(best, (t[u]<= s[i]?0:t[u]-s[i])+solve(i, bit|(1<<i)));
	}
	return dp[u][bit] = best;
}

int col[maxN];

void ff(int u)
{
	col[u] = 1;
	for(int v : adj[u])
	{
		if(!col[v]) ff(v);
	}
}

ll plan_roller_coaster(vector<int> S, vector<int> T)
{
	n = S.size();
	for(int i = 0; i< n; i++)
	{
		s[i] = S[i];
		t[i] = T[i];
	}
	if(n<= 16)
	{
		memset(dp, -1, sizeof dp);
		ll best = 1e18;
		for(int i = 0; i< n; i++) best = min(best, solve(i, 1<<i));
		return best;
	}
	vector<int> all;
	for(int i = 0; i< n; i++)
	{
		all.pb(s[i]); all.pb(t[i]);
	}
	all.pb(1); all.pb(1e9);
	sort(all.begin(), all.end());
	all.resize(unique(all.begin(), all.end())-all.begin());
	for(int i = 0; i< (int) all.size(); i++) adj[i].clear();
	sw[0]++;
	sw[all.size()-1]--;
	adj[all.size()-1].pb(0);
	for(int i = 0; i< n; i++)
	{
		int ss = lower_bound(all.begin(), all.end(), s[i])-all.begin();
		int tt = lower_bound(all.begin(), all.end(), t[i])-all.begin();
		sw[ss]--;
		sw[tt]++;
		adj[ss].pb(tt);
	}
	int run = 0;
	for(int i = 0; i< (int) all.size(); i++)
	{
		if(run> 0 && i)
		{
			adj[i-1].pb(i);
		}
		run += sw[i];
		if(run< 0) return 12345678;
	}
	memset(col, 0, sizeof col);
	ff(0);
	for(int i = 0; i< (int) all.size(); i++) if(!col[i]) return 12345678;
	return 0;
}

• Subtask 1: 11 / 11
• Subtask 2: 23 / 23
• Subtask 3: 0 / 30
• Subtask 4: 0 / 36