Submission #62410

#	Time	Username	Problem	Language	Result	Execution time	Memory
62410		fallingstar	Shortcut (IOI16_shortcut)	C++14	0 / 100	3 ms	676 KiB

shortcut

#include "shortcut.h"
#include <iostream>
#include <algorithm>

#define long long long

using namespace std;

const int N = 1e6 + 2;
const int LN = 20;
const long INF = 1LL << 60;

int n, sec[N];
long dmain[N], express;
int rmqp[LN][N], rmqs[LN][N];

void BuildRMQ()
{
    for (int i = 0; i < n; ++i)
        rmqp[0][i] = rmqs[0][i] = i;

    for (int j = 1; j < LN; ++j)
        for (int i = 0; i + (1 << j) <= n; ++i)
        {
            rmqp[j][i] = max(rmqp[j - 1][i], rmqp[j - 1][i + (1 << (j - 1))], [](int x, int y) {
                return dmain[x] + sec[x] < dmain[y] + sec[y];
            });
            rmqs[j][i] = max(rmqs[j - 1][i], rmqs[j - 1][i + (1 << (j - 1))], [](int x, int y) {
                return -dmain[x] + sec[x] < -dmain[y] + sec[y];
            });
        }
}

int QueryPref(int l, int r)
{
    int k = 31 - __builtin_clz(r - l + 1);
    return max(rmqp[k][l], rmqp[k][r - (1 << k) + 1], [](int x, int y) {
                return dmain[x] + sec[x] < dmain[y] + sec[y];
            });
}
int QuerySuff(int l, int r)
{
    int k = 31 - __builtin_clz(r - l + 1);
    return max(rmqs[k][l], rmqs[k][r - (1 << k) + 1], [](int x, int y) {
                return -dmain[x] + sec[x] < -dmain[y] + sec[y];
            });
}
inline long GetPref(int l, int r)
{
    if (l > r) return -INF;
    int u = QueryPref(l, r);
    return dmain[u] + sec[u];
}
inline long GetSuff(int l, int r)
{
    if (l > r) return -INF;
    int u = QuerySuff(l, r);
    return dmain[n - 1] - dmain[u] + sec[u];
}

long fsuff[N], fpref[N];

bool Maximize(long &a, long b) { if (a >= b) return false; a = b; return true; }
inline long Dist(int u, int v) { return abs(dmain[v] - dmain[u]); }

void Prep()
{
    BuildRMQ();
    fsuff[n - 1] = sec[n - 1];
    for (int i = n - 2; i >= 0; --i)
        fsuff[i] = max(fsuff[i + 1], GetPref(i + 1, n - 1) - dmain[i] + sec[i]);
    fpref[0] = sec[0];
    for (int i = 1; i < n; ++i)
        fpref[i] = max(fpref[i - 1], GetSuff(0, i - 1) - Dist(i, n - 1) + sec[i]);
}

bool GetAns(int u, int v, long &ans)
{
    if (u > v) swap(u, v);

    bool glob_r = false;
    ans = max(fsuff[v], fpref[u]);

    long tmp = sec[u];
    sec[u] = GetSuff(0, u) - Dist(u, n - 1);

    for (int i = u, midR = u; i < v; ++i)
    {
        long distR = 0;
        bool loc_r = false;

        while (midR < v && Dist(i, midR + 1) < Dist(midR + 1, v) + express + Dist(u, i)) ++midR;
        if (Maximize(distR, GetPref(v, n - 1) - dmain[v] + min(express + Dist(u, i), Dist(v, i)))) loc_r = true;

        if (Maximize(distR, GetSuff(midR + 1, v) - Dist(n - 1, v) + express + Dist(u, i))) loc_r = false;
        if (Maximize(distR, GetPref(i + 1, midR) - dmain[i])) loc_r = false;

        if (Maximize(ans, sec[i] + distR)) glob_r = loc_r;
    }

    sec[u] = tmp;
    return glob_r;
}

long find_shortcut(int n_, vector<int> a_, vector<int> d_, int c_)
{
    n = n_, express = c_;
    for (int i = 1; i < n; ++i)
        dmain[i] = dmain[i - 1] + a_[i - 1];
    copy(d_.begin(), d_.end(), sec);
    Prep();

    long res;
    GetAns(0, 1, res);
    for (int l = 0; l + 1 < n; ++l)
    {
        int lo = l + 1, hi = n - 1;
        while (lo <= hi)
        {
            int mid = (lo + hi) / 2;
            long val = INF;
            if (Dist(l, mid) <= express || GetAns(l, mid, val)) lo = mid + 1;
            else hi = mid - 1;
            res = min(res, val);
        }
//        cout << "#" << l << ' ' << lo << ' ' << hi << ' ' << '\n';
    }
//    for (int i = 0; i < n; ++i)
//        for (int j = i + 1; j < n; ++j)
//        {
//            long val = INF;
//            GetAns(i, j, val);
//            if (Dist(i, j) <= express) continue;
////            cout << i << ' ' << j << ' ' << val << '\n';
//            res = min(res, val);
//        }
    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