Submission #787606

#	Time	Username	Problem	Language	Result	Execution time	Memory
787606		ymm	Shortcut (IOI16_shortcut)	C++17	71 / 100	1198 ms	2352 KiB

shortcut

#include "shortcut.h"
#include <bits/stdc++.h>
#define Loop(x,l,r) for (ll x = (l); x < (r); ++x)
#define LoopR(x,l,r) for (ll x = (r)-1; x >= (l); --x)
typedef long long ll;
typedef std::pair<ll,ll> pll;
using namespace std;

const int N = 3030;
ll ps[N], a[N], C;
int n;

ll calcin(int l, int r)
{
#if 0
	ll ans = 0;
	Loop (i,l,r+1) Loop (j,i+1,r+1) {
		ll x = ps[j] - ps[i];
		ll y = ps[r] - ps[j] + ps[i] - ps[l] + C;
		ans = max(ans, min(x, y) + a[i] + a[j]);
	}
	return ans;
#endif
	int p = l;
	vector<int> vec;
	int vecp = 0;
	auto cw = [&](int i, int j) {
		assert(l <= i && i <= r && l <= j && j <= r);
		if (i == j)
			return 0;
		int x = min(i, j);
		int y = max(i, j);
		ll v1 = ps[y] - ps[x];
		ll v2 = C + ps[r] - ps[y] + ps[x] - ps[l];
		if (v1 == v2)
			return 1;
		return (v1 < v2) ^ (i > j);
	};
	auto dis = [&](int i, int j) {
		assert(l <= i && i <= r && l <= j && j <= r);
		if (i < j)
			return ps[j] - ps[i] + a[j] + a[i];
		else
			return C + ps[r] - ps[i] + ps[j] - ps[l] + a[i] + a[j];
	};
	auto mod = [&](int x) {
		return (x-l)%(r-l+1)+l;
	};
	ll ans = 0;
	Loop (i,l,r+1) {
		p = max<int>(p, i+1);
		while (vecp < vec.size() && vec[vecp] <= i)
			++vecp;
		while (cw(i, mod(p))) {
			while (vecp < vec.size() && dis(i, mod(vec.back())) <= dis(i, mod(p)))
				vec.pop_back();
			vec.push_back(p);
			++p;
		}
		if (vecp < vec.size()) {
			ans = max(ans, dis(i, mod(vec[vecp])));
			//cerr << i << ' ' << mod(vec[vecp]) << ' ' << dis(i, mod(vec[vecp])) << '\n';
		}
	}
	return ans;
}

ll calc0(int l, int r)
{
	ll ans = calcin(l, r);
	ll mx = -1e18;
	Loop (i,0,l) {
		ans = max(ans, ps[i] + a[i] + mx);
		mx = max(mx, a[i] - ps[i]);
	}
	Loop (i,l,r+1) {
		ll x = min(ps[i], ps[r] - ps[i] + ps[l] + C);
		ans = max(ans, a[i] + x + mx);
	}
	return ans;
}
ll calcn(int l, int r)
{
	ll ans = 0;
	ll mx = -1e18;
	LoopR (i,r+1,n) {
		ans = max(ans, a[i] - ps[i] + mx);
		mx = max(mx, a[i] + ps[i]);
	}
	LoopR (i,l,r+1) {
		ll x = min(-ps[i], -ps[r] + ps[i] - ps[l] + C);
		ans = max(ans, a[i] + x + mx);
	}
	LoopR (i,0,l) {
		ll x = min(0ll, C - (ps[r] - ps[l]));
		ans = max(ans, a[i] - ps[i] + mx + x);
	}
	return ans;
}

long long find_shortcut(int _n, std::vector<int> l, std::vector<int> d, int c)
{
	n = _n;
	Loop (i,1,n)
		ps[i] = ps[i-1] + l[i-1];
	Loop (i,0,n)
		a[i] = d[i];
	C = c;
	ll ans = 1e18;
	int p0 = 0, p1 = 1;
	while (p0 < n-1) {
		ll a = calc0(p0, p1);
		ll b = calcn(p0, p1);
		ans = min(ans, max(a, b));
		if (a <= b) {
			++p1;
		}
		if (a > b || p1 == n) {
			++p0;
			p1 -= 4;
		}
		while (p0 >= p1)
			++p1;
	}
	//Loop (i,0,n-1) {
	//	int l = i+1, r = n-1;
	//	while (l < r) {
	//		int j = (l+r+1)/2;
	//		if (a <= b)
	//			l = j;
	//		else
	//			r = j-1;
	//	}
	//	ans = min(ans, max(calc0(i, l), calcn(i, l)));
	//	if (l < n-1)
	//		ans = min(ans, max(calc0(i, l+1), calcn(i, l+1)));
	//}
	return ans;
}

Compilation message (stderr)

shortcut.cpp: In function 'll calcin(int, int)':
shortcut.cpp:52:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   52 |   while (vecp < vec.size() && vec[vecp] <= i)
      |          ~~~~~^~~~~~~~~~~~
shortcut.cpp:55:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   55 |    while (vecp < vec.size() && dis(i, mod(vec.back())) <= dis(i, mod(p)))
      |           ~~~~~^~~~~~~~~~~~
shortcut.cpp:60:12: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   60 |   if (vecp < vec.size()) {
      |       ~~~~~^~~~~~~~~~~~

• Subtask 1: 9 / 9
• Subtask 2: 14 / 14
• Subtask 3: 8 / 8
• Subtask 4: 7 / 7
• Subtask 5: 33 / 33
• Subtask 6: 0 / 22
• Subtask 7: 0 / 4
• Subtask 8: 0 / 3