Submission #105465

#	Time	Username	Problem	Language	Result	Execution time	Memory
105465		polyfish	Roller Coaster Railroad (IOI16_railroad)	C++14	34 / 100	206 ms	15372 KiB

railroad

//Pantyhose(black) + glasses = infinity

#include <bits/stdc++.h>
using namespace std;
 
#define debug(x) cerr << #x << " = " << x << '\n';
#define BP() cerr << "OK!\n";
#define PR(A, n) {cerr << #A << " = "; for (int _=1; _<=n; ++_) cerr << A[_] << ' '; cerr << '\n';}
#define PR0(A, n) {cerr << #A << " = "; for (int _=0; _<n; ++_) cerr << A[_] << ' '; cerr << '\n';}
#define FILE_NAME "data"

const int64_t INF = 1e18;

int n;
vector<pair<int, int> > a;
int64_t f[1<<16][16];

int64_t dp(int mask, int last) {
	if (__builtin_popcount(mask)==n)
		return 0;

	if (f[mask][last]>-1)
		return f[mask][last];

	int64_t res = INF;

	for (int i=0; i<n; ++i) {
		if (((mask>>i) & 1)==0) {
			int new_mask = mask | (1<<i);
			// if (mask==11 && last==1 && i==2)
			// 	debug();
			res = min(res, dp(new_mask, i) + max(0, a[last].second - a[i].first));
		}
	}

	return f[mask][last] = res;
}

bool cmp(pair<int, int> l1, pair<int, int> l2) {
	return l1 > l2;
}

bool check() {
	vector<int> L(n);

	for (int i=0; i<n; ++i)
		L[i] = upper_bound(a.begin(), a.end(), make_pair(a[i].second, 0), cmp) - a.begin() - 1;
	// PR0(L, L.size());

	set<int> avail;
	for (int i=0; i<n; ++i)
		avail.insert(i);

	int cur = n-1;
	avail.erase(n-1);

	for (int i=0; i+1<n; ++i) {
		// debug(cur);
		auto it = avail.upper_bound(L[cur]);

		if (it==avail.begin())
			return false;

		--it;
		cur = *it;
		avail.erase(*it);
	}

	return true;
}

int64_t plan_roller_coaster(vector<int> s, vector<int> t) {
	n = s.size();
	a.resize(n);

	for (int i=0; i<n; ++i)
		a[i] = {s[i], t[i]};
	sort(a.begin(), a.end(), greater<pair<int, int> >());

	if (n<=16) {
		memset(f, -1, sizeof(f));
		// debug(dp(1, 0));

		int64_t res = INF;
		for (int i=0; i<n; ++i)
			res = min(res, dp(1<<i, i));
		
		return res;
	}

	return check();
}

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