Submission #787601

#	Time	Username	Problem	Language	Result	Execution time	Memory
787601		Sohsoh84	Shortcut (IOI16_shortcut)	C++17	0 / 100	1 ms	1236 KiB

shortcut

#include "shortcut.h"
#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

#define sep		' '
#define debug(x)	cerr << #x << ": " << x << endl; 

const ll MAXN = 3000 + 10;
const ll INF = 3e18;

int n;
ll fans, L[MAXN], ps[MAXN], D[MAXN], XT[MAXN], XS[MAXN], c, mx_xt[MAXN], mx_xs[MAXN], f1[MAXN], f2[MAXN], FT[MAXN][MAXN], FS[MAXN][MAXN];

inline ll dist(int i, int j) {
	if (i > j) swap(i, j);
	return ps[j] - ps[i];
}

inline ll solve(int l, int r) {
	ll ans = 0;
	if (r < l) return INF;
	if (c >= dist(l, r)) return INF;

	ans = max(ans, mx_xs[l] + mx_xt[r] - dist(l, r) + c);
	
	int p = l;
	ll f = dist(l, r) + c;
	for (int i = l; i <= r; i++) {
		ans = max(ans, min(dist(l, i), dist(i, r) + c) + ps[l] + mx_xs[(i == l ? l - 1 : l)] + D[i]);
		ans = max(ans, min(dist(r, i), dist(i, l) + c) - ps[r] + mx_xt[(i == r ? r + 1 : r)] + D[i]);
		
		while (dist(p, i) > f / 2)
			p++;

		if (p < i) ans = max(ans, XT[i] + FS[p][i - 1]);
		if (l < p) ans = max(ans, f + XS[i] + FT[l][p - 1]);
	}

	ans = max(ans, f1[l - 1]);
	ans = max(ans, f2[r + 1]);

	return ans;
}

inline void divide(int l, int r, int optl, int optr) {
	if (r < l) return;
	int mid = (l + r) >> 1;

	int opt = optl;
	ll ans = INF;
	for (int i = optl; i <= optr; i++) {
		ll tans = solve(i, mid);
		if (tans < ans) {
			opt = i;
			ans = tans;
		}
	}
	
	fans = min(fans, ans);
	divide(l, mid - 1, optl, opt);
	divide(mid + 1, r, opt, optr);
}


ll find_shortcut(int n_, vector<int> l_, vector<int> d_, int c_) {
	n = n_;
	c = c_;

	for (int i = 0; i < MAXN; i++)
		mx_xt[i] = mx_xs[i] = f1[i] = f2[i] = -INF;

	for (int i = 1; i <= n; i++) {
		L[i] = l_[i - 1];
		D[i] = d_[i - 1];
		if (i < n) ps[i + 1] = ps[i] + L[i];

		XS[i] = D[i] - ps[i];
		XT[i] = D[i] + ps[i];

		mx_xs[i] = max(mx_xs[i - 1], XS[i]);

		f1[i] = max(f1[i - 1], XT[i] + mx_xs[i - 1]);
	}

	for (int i = n; i > 0; i--) {
		mx_xt[i] = max(mx_xt[i + 1], XT[i]);
		f2[i] = max(f2[i + 1], XS[i] + mx_xt[i + 1]);
	}

	for (int i = 1; i <= n;  i++) {
		FT[i][i] = XT[i];
		FS[i][i] = XS[i];
		
		for (int j = i + 1; j <= n; j++) {
			FT[i][j] = max(FT[i][j - 1], XT[j]);
			FS[i][j] = max(FS[i][j - 1], XS[j]);
		}
	}

/*	for (int i = 1; i <= n; i++) {
		for (int j = i + 1; j <= n; j++)
			cerr << solve(i, j) << sep;
		
		cerr << endl;
	}
*/
	fans = 0;
	for (int i = 1; i <= n; i++)
		for (int j = i + 1; j <= n; j++)
			fans = max(fans, dist(i, j) + D[i] + D[j]);

	
	for (int i = 1; i <= n; i++) {
		int l = i, r = n;
		while (l < r) {
			int mid = (l + r) >> 1;
			if (solve(i, mid) >= solve(i, mid + 1)) l = mid + 1;
			else r = mid;
		}

		fans = min(fans, solve(i, l));
	}

	divide(1, n, 1, n);
	return fans;
}

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