Submission #140832

#	Time	Username	Problem	Language	Result	Execution time	Memory
140832		Namnamseo	Shortcut (IOI16_shortcut)	C++17	97 / 100	2060 ms	84596 KiB

shortcut

#include "shortcut.h"
#include <bits/stdc++.h>
using namespace std;
using ll=long long;
using pll=pair<ll,ll>;
#define all(x) x.begin(), x.end()
#define x first
#define y second

const int maxn = int(1e6) + 10;

int n;
int C;
ll pos[maxn];
ll d[maxn];

pll rpdr[maxn];
pll lmdl[maxn];

const ll inf = 1ll<<60;

struct BoundSys {
	pll mx, smx;
	void init(){ mx = smx = {-inf, -1}; }
	BoundSys(){ init(); }
	void upd(ll val, ll idx) {
		pll t(val, idx);
		if(mx < t) smx = mx, mx = t;
		else if(smx < t) smx = t;
	}
	ll get_max(ll idx) {
		if(mx.y != -1 && mx.y != idx) return mx.x;
		else if(smx.y != -1) return smx.x;
		else return -inf;
	}
};

struct Gug {
	BoundSys bl, br;
	ll rL, rR;
	Gug(){ bl.init(); br.init(); rL = -inf; rR = +inf; }
	void Add(ll lv, ll rv, ll i) { bl.upd(lv, i); br.upd(-rv, i); }
	void upd(ll lv, ll rv, ll i) {
		rL = max(rL, bl.get_max(i) + lv);
		rR = min(rR, -br.get_max(i) + rv);
	}
};

bool f(ll X) {
	int lst = n;
	Gug ipj, imj;
	auto Add = [&](int r) {
		ipj.Add(pos[r] + d[r], pos[r]-d[r], r);
		imj.Add(d[r] - pos[r], -d[r]-pos[r], r);
	};

	auto Upd = [&](int l) {
		ipj.upd(pos[l] + d[l] + C-X, pos[l] - d[l] + X-C, l);
		imj.upd(pos[l] + d[l] + C-X, pos[l] - d[l] + X-C, l);
	};

	for(int i=n-1; 0<=i; --i) {
		while(lst-1 >= 0 && rpdr[lst-1].x > lmdl[i].x + X) {
			--lst;
			Add(rpdr[lst].y);
		}

		Upd(lmdl[i].y);
	}

	int jminp = 0, jminm = 0;
	int jmaxp = n-1, jmaxm = n-1;

	while(jminp < n && pos[jminp] < ipj.rL-pos[0]) ++jminp;
	while(jmaxm >= 0 && pos[jmaxm] > pos[0]-imj.rL) --jmaxm;

	for(int i=0; i<n; ++i) {
		ll pi = pos[i];

		while(jminp >= 1 && pos[jminp-1] >= ipj.rL-pi) --jminp;

		while(jminm < n && pos[jminm] < pi-imj.rR) ++jminm;

		while(jmaxp >= 0 && pos[jmaxp] > ipj.rR-pi) --jmaxp;

		while(jmaxm+1 < n && pos[jmaxm+1] <= pi-imj.rL) ++jmaxm;

		if(max(jminp, jminm) <= min(jmaxp, jmaxm)) {
			return 1;
		}
	}

	return 0;
}

long long find_shortcut(int _n, std::vector<int> l, std::vector<int> _d, int c)
{
	n = _n;
	C = c;
	copy(all(_d), d);
	for(int i=1; i<n; ++i) pos[i] = pos[i-1] + l[i-1];

	for(int i=0; i<n; ++i) {
		rpdr[i] = {pos[i] + d[i], i};
		lmdl[i] = {pos[i] - d[i], i};
	}

	sort(rpdr, rpdr+n);
	sort(lmdl, lmdl+n);

	ll L = 0, R = 2e16;
	ll pmx = 0;
	for(int i=0; i<n; ++i) {
		if(i)
			L = max(L, d[i] + pmx);
		pmx = max(pmx, d[i]);
	}

	while(L+1 < R) {
		ll mid = (L+R) / 2;
		if(f(mid)) R = mid;
		else L = mid;
	}

	return R;
}

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