Submission #54167

#	Time	Username	Problem	Language	Result	Execution time	Memory
54167		aome	Shortcut (IOI16_shortcut)	C++17	0 / 100	3 ms	712 KiB

shortcut

#include "shortcut.h"

#include <bits/stdc++.h>

using namespace std;

const int N = 505;
const long long INF = 1e18;

int n, c, a[N];
long long f1[N][N];
long long f2[N][N];
long long res;
long long dis[N];

long long solve(int l, int r) {
	long long maxDis = 0;
	// two points outside [l, r]
	for (int i = r + 1; i < n; ++i) {
		if (l - 1 >= 0) {
			maxDis = max(maxDis, dis[i] + a[i] + f2[0][l - 1] + min(0LL, c - dis[r] + dis[l]));
		}
		if (r + 1 <= i - 1) {
			maxDis = max(maxDis, dis[i] + a[i] + f2[r + 1][i - 1]);
		}
	}
	for (int i = 1; i < l; ++i) {
		maxDis = max(maxDis, dis[i] + a[i] + f2[0][i - 1]);
	}
	// one point inside [l, r] and one point outside [l, r]
	for (int i = l; i <= r; ++i) {
		// from i to one point inside [0, l - 1]
		if (l - 1 >= 0) {
			maxDis = max(maxDis, min(dis[i], dis[r] - dis[i] + c + dis[l]) + a[i] + f2[0][l - 1]);
		}
		// from i to to one point inside [r + 1, n - 1]
		if (r + 1 < n) {
			maxDis = max(maxDis, f1[r + 1][n - 1] + a[i] + min(-dis[i], dis[i] - dis[l] + c - dis[r]));
		}
	} 
	// // two points inside [l, r]
	int ptr = l;
	for (int i = l; i <= r; ++i) {
		while (ptr < i && dis[r] - dis[l] - dis[i] + dis[ptr] + c < dis[i] - dis[ptr]) ptr++;
		if (ptr != l) maxDis = max(maxDis, a[i] + dis[r] - dis[l] - dis[i] + f1[l][ptr - 1] + c);
		if (ptr != i) maxDis = max(maxDis, a[i] + dis[i] + f2[ptr][i - 1]);
	}
	return maxDis;
}

long long find_shortcut(int _n, vector<int> l, vector<int> d, int _c) {
	n = _n, c = _c;
	for (int i = 0; i < n; ++i) a[i] = d[i];
    for (int i = 1; i < n; ++i) dis[i] = dis[i - 1] + l[i - 1];
    for (int i = 0; i < n; ++i) {
    	f1[i][i] = dis[i] + a[i];
    	f2[i][i] = -dis[i] + a[i];
    	for (int j = i + 1; j < n; ++j) {
    		f1[i][j] = max(f1[i][j - 1], dis[j] + a[j]);
    		f2[i][j] = max(f2[i][j - 1], -dis[j] + a[j]);
    	}
    }
    res = INF;
    int ptr = 0;
    long long opt = INF;
    for (int i = 1; i < n; ++i) {
    	long long tmp = solve(0, i);
    	if (opt > tmp) {
    		opt = tmp, ptr = i;
    	} 
    }
    res = min(res, opt);
    for (int i = 1; i < (n - 1); ++i) {
    	long long x = solve(i, ptr);
    	while (ptr + 1 < n) {
    		long long y = solve(i, ptr + 1);
    		if (x > y) {
    			x = y, ptr++;
    		}
    		else break;
    	}
    	res = min(res, x);
    }
    return res;
}

• 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