Submission #807486

#	Time	Username	Problem	Language	Result	Execution time	Memory
807486		happypotato	Roller Coaster Railroad (IOI16_railroad)	C++17	0 / 100	165 ms	22852 KiB

railroad

#include "railroad.h"

#include <bits/stdc++.h>
using namespace std;
#define int long long
#define pii pair<int, int>
#define ff first
#define ss second

vector<int> s, t;
int n;

int BruteDP() {
	int dp[(1 << n)][n];
	for (int conf = 0; conf < (1 << n); conf++) {
		for (int i = 0; i < n; i++) {
			dp[conf][i] = (conf == (1 << i) ? 0 : 1e18); 
		}
	}
	for (int bit = 2; bit <= n; bit++) {
		for (int conf = 0; conf < (1 << n); conf++) {
			if (__builtin_popcountll(conf) != bit) continue;
			for (int i = 0; i < n; i++) {
				if (conf & (1 << i)) {
					for (int j = 0; j < n; j++) {
						if (!bool(conf & (1 << j)) || i == j) continue;
						dp[conf][i] = min(dp[conf][i], dp[conf ^ (1 << i)][j] + max(0LL, t[j] - s[i]));
					}
				}
			}
		}
	}
	int ans = 1e18;
	for (int i = 0; i < n; i++) ans = min(ans, dp[(1 << n) - 1][i]);
	return ans;
}



long long plan_roller_coaster(vector<int32_t> S, vector<int32_t> T) {
	n = S.size(); s.resize(n); t.resize(n);
	for (int i = 0; i < n; i++) {
		s[i] = S[i]; t[i] = T[i];
	}
	// for (int i = 0; i < n; i++) cerr << s[i] << ' '; cerr << endl;
	// for (int i = 0; i < n; i++) cerr << t[i] << ' '; cerr << endl;

	// if (n <= 16) return BruteDP();

	vector<pii> v(n);
	for (int i = 0; i < n; i++) {
		v[i] = {s[i], t[i]};
	}
	sort(v.begin(), v.end(), greater<pii>());
	set<int> s;
	for (int i = 0; i < n; i++) s.insert(i);
	int cur = n - 1;
	for (int turns = 0; turns < n; turns++) {
		s.erase(s.find(cur));
		if (turns == n - 1) return 0;
		int tar = v[cur].ss;
		int lb = 0, rb = n - 1;
		while (lb < rb) {
			int mid = (lb + rb + 1) >> 1;
			if (v[mid].ff >= tar) lb = mid;
			else rb = mid - 1;
		}
		int pos = lb;
		set<int>::iterator it = s.upper_bound(pos);
		if (it == s.begin()) return 1;
		cur = *(--it);
	}
}

#undef int

Compilation message (stderr)

railroad.cpp: In function 'long long int plan_roller_coaster(std::vector<int>, std::vector<int>)':
railroad.cpp:50:17: warning: control reaches end of non-void function [-Wreturn-type]
   50 |  vector<pii> v(n);
      |                 ^

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