Submission #526148

#	Time	Username	Problem	Language	Result	Execution time	Memory
526148		PurpleCrayon	Comparing Plants (IOI20_plants)	C++17	25 / 100	4082 ms	184584 KiB

plants

#include "plants.h"
#include <bits/stdc++.h>
using namespace std;

#define sz(v) int(v.size())
const int INF = 1e9+10;

int n, k;
vector<int> a, b;
vector<int> nxt, prv;

void init(int K, vector<int> r) {
    n = sz(r), k = K;
    vector<bool> done(n);


    a.resize(n);
    nxt.assign(2*n, -1), prv.assign(2*n, -1);

    set<int> cand;
    set<int> bad_cand;
    auto prv_cand = [&](int x, bool which) {
        auto& use = (which ? cand : bad_cand);
        if (!sz(use)) return INF;
        auto it = use.lower_bound(x);
        if (it != use.begin()) return *prev(it);
        return *use.rbegin();
    };
    auto nxt_cand = [&](int x, bool which) {
        auto& use = (which ? cand : bad_cand);
        if (!sz(use)) return INF;
        auto it = use.upper_bound(x);
        if (it == use.end()) return *use.begin();
        return *it;
    };
    auto forward_dist = [&](int a, int b) {
        if (a == INF || b == INF) return INF;
        if (a < b) return b - a;
        return n - a + b;
    };

    vector<bool> has_add(n);
    for (int i = 0; i < n; i++) if (!r[i])
        cand.insert(i), has_add[i] = 1;

    vector<vector<int>> stop(n);
    for (int i = 0; i < n; i++) if (!r[i]) {
        int p = prv_cand(i, true);
        if (forward_dist(p, i) < k) {
            stop[p].push_back(i);
            bad_cand.insert(i);
        }
    }
    for (int x : bad_cand) cand.erase(x);

    auto prv_cand_both = [&](int x) {
        int one = prv_cand(x, true), two = prv_cand(x, false);
        if (forward_dist(one, x) < forward_dist(two, x)) return one;
        return two;
    };
    auto nxt_cand_both = [&](int x) {
        int one = nxt_cand(x, true), two = nxt_cand(x, false);
        if (forward_dist(x, one) < forward_dist(x, two)) return one;
        return two;
    };

    auto add_cand = [&](int x) {
        // cerr << "add_cand(" << x << ")\n";
        int p = prv_cand_both(x);
        if (p != INF && forward_dist(p, x) < k) {
            stop[p].push_back(x);
            cand.erase(x);
            bad_cand.insert(x);
        } else {
            bad_cand.erase(x);
            cand.insert(x);
        }
        int q = nxt_cand_both(x);
        if (q != INF && forward_dist(x, q) < k) {
            stop[x].push_back(q);
            cand.erase(q);
            bad_cand.insert(q);
        }

        // cerr << "AA: ";
        // for (int x : cand) cerr << x << ' ';
        // cerr << endl;

        // cerr << "BB: ";
        // for (int x : bad_cand) cerr << x << ' ';
        // cerr << endl;
    };

    for (int rep = 0; rep < n; rep++) {
        int me = *cand.begin();
        // cerr << "> " << me << endl;

        a[me] = n - 1 - rep;
        done[me] = 1;
        cand.erase(me);

        for (int x : stop[me]) if (!done[x]) {
            add_cand(x);
        }

        for (int i = me - k + 1; i < me; i++) { // range add, range min
            int c = (i + n) % n;
            if (!has_add[c]) {
                r[c]--;
                if (r[c] == 0) {
                    add_cand(c);
                    has_add[c] = 1;
                }
            }
        }
        // cerr << "A: ";
        // for (int x : cand) cerr << x << ' ';
        // cerr << endl;

        // cerr << "B: ";
        // for (int x : bad_cand) cerr << x << ' ';
        // cerr << endl;
    }
    for (int rep : {0, 1}) for (int x : a) b.push_back(x);

    assert(sz(b) == 2 * n);
    for (int i = 0; i < 2*n; i++) {
        for (int j = i+1; j < min(2*n, i+k); j++) { // range min
            if (b[j] > b[i] && (nxt[i] == -1 || b[nxt[i]] > b[j]))
                nxt[i] = j;
        }
        for (int j = max(0, i-k+1); j < i; j++) { // range min
            if (b[j] > b[i] && (prv[i] == -1 || b[prv[i]] > b[j]))
                prv[i] = j;
        }
    }
}

bool can_nxt(int x, int y) {
    int c = x;
    int need = y < x ? y + n : y;
    while (nxt[c] != -1 && nxt[c] <= need) {
        assert(b[nxt[c]] > b[c]);
        c = nxt[c];
    }
    assert(b[need] == a[y]);
    return need - c < k && b[need] >= b[c];
}
bool can_prv(int x, int y) {
    int c = x > y ? x : x + n;
    int need = y;
    while (prv[c] != -1 && prv[c] >= need) {
        assert(b[prv[c]] > b[c]);
        c = prv[c];
    }
    assert(b[need] == a[y]);
    return c - need < k && b[need] >= b[c];
}
bool can_reach(int x, int y) {
    return can_nxt(x, y) || can_prv(x, y);
}

int compare_plants(int x, int y) {
    if (can_reach(x, y)) { // y is greater than x
        assert(a[y] > a[x]);
        return -1;
    }
    if (can_reach(y, x)) { // x is greater than y
        assert(a[x] > a[y]);
        return 1;
    }
    return 0;
}

Compilation message (stderr)

plants.cpp: In function 'void init(int, std::vector<int>)':
plants.cpp:124:14: warning: unused variable 'rep' [-Wunused-variable]
  124 |     for (int rep : {0, 1}) for (int x : a) b.push_back(x);
      |              ^~~

• Subtask 1: 0 / 5
• Subtask 2: 14 / 14
• Subtask 3: 0 / 13
• Subtask 4: 0 / 17
• Subtask 5: 11 / 11
• Subtask 6: 0 / 15
• Subtask 7: 0 / 25