Submission #755910

#	Time	Username	Problem	Language	Result	Execution time	Memory
755910		MilosMilutinovic	송신탑 (IOI22_towers)	C++17	0 / 100	4075 ms	19796 KiB

towers

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

const int N = 1e5 + 10;
vector<vector<int>> vec;

namespace sparse {
    int n;
    vector<int> logs;
    vector<vector<int>> st;
    void build(vector<int> h) {
        n = (int) h.size();
        logs.resize(n + 1);
        st.resize(n);
        for (int i = 0; i < n; i++) {
            st[i].resize(20);
            st[i][0] = h[i];
        }
        for (int j = 1; j < 20; j++)
            for (int i = 0; i + (1 << j) <= n; i++)
                st[i][j] = max(st[i][j - 1], st[i + (1 << (j - 1))][j - 1]);
        for (int i = 2; i <= n; i++) logs[i] = logs[i >> 1] + 1;
    }
    int query(int l, int r) {
        int k = logs[r - l + 1];
        return max(st[l][k], st[r - (1 << k) + 1][k]);
    }
};

void init(int n, vector<int> h) {
    vector<int> l_id(n), r_id(n);
    vector<int> stk;
    for (int i = 0; i < n; i++) {
        while (!stk.empty() && h[i] < h[stk.back()]) {
            stk.pop_back();
        }
        l_id[i] = (stk.empty() ? -1 : stk.back());
        stk.push_back(i);
    }
    stk.clear();
    for (int i = n - 1; i >= 0; i--) {
        while (!stk.empty() && h[i] < h[stk.back()]) {
            stk.pop_back();
        }
        r_id[i] = (stk.empty() ? -1 : stk.back());
        stk.push_back(i);
    }
    sparse::build(h);
    vector<int> order(n);
    iota(order.begin(), order.end(), 0);
    sort(order.begin(), order.end(), [&](int i, int j) { return h[i] < h[j]; });
    for (int _i = 1; _i < n; _i++) {
        int i = order[_i];
        int d = 1e9;
        if (l_id[i] != -1)
            d = min(d, sparse::query(l_id[i], i) - h[i]);
        if (r_id[i] != -1)
            d = min(d, sparse::query(i, r_id[i]) - h[i]);
//        assert(d != 0);
//        printf("%d %d\n", i + 1, d);
        vec.push_back({d, i, l_id[i], r_id[i]});
    }
    sort(vec.begin(), vec.end());
}

int find_first(int x) {
    int l = 0, r = vec.size() - 1, p = vec.size();
    while (l <= r) {
        int mid = l + r >> 1;
        if (vec[mid][0] >= x)
            r = mid - 1, p = mid;
        else
            l = mid + 1;
    }
    return vec.size() - p;
}

int get(int i) { return sparse::query(i, i); }

bool taken[N];

int get_mn_idx(int l, int r) {
    int idx = l;
    for (int i = l; i <= r; i++)
        if (get(i) < get(idx))
            idx = i;
    return idx;
}

int max_towers(int l, int r, int d) {
    vector<int> ids;
    for (auto& p : vec)
        if (p[0] >= d && l <= p[1] && p[1] <= r)
            ids.push_back(p[1]), taken[p[1]] = true;
    sort(ids.begin(), ids.end());
    int idx = l;
    for (int i = l; i <= r; i++) {
        if (get(i) < get(idx)) {
            idx = i;
        }
    }
    function<void(int)> Try = [&](int idx) {
        if (taken[idx])
            return;
        int L = l - 1, R = r + 1;
        int ans = ids.size();
        for (int i : ids) {
            if (i < idx)
                L = max(L, i);
            else
                R = min(R, i);
        }
        bool ok = true;
        if (L >= l && max(get(L), get(idx)) > sparse::query(L, idx) - d)
            ok = false;
        if (R <= r && max(get(R), get(idx)) > sparse::query(idx, R) - d)
            ok = false;
        if (ok)
            taken[idx] = true, ids.push_back(idx);
    };
    int first_l = l;
    while (first_l <= r && !taken[first_l])
        first_l++;
    int first_r = r;
    while (first_r >= l && !taken[first_r])
        first_r--;
    if (first_l > l)
        Try(get_mn_idx(l, first_l - 1));
    if (first_r < r)
        Try(get_mn_idx(first_r + 1, r));
    Try(get_mn_idx(l, r));
    for (int i : ids)
        taken[i] = false;
    return ids.size();
}


/*
7 3
10 20 60 40 50 30 70
1 5 10
2 2 100
0 6 17
*/

Compilation message (stderr)

towers.cpp: In function 'int find_first(int)':
towers.cpp:70:21: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   70 |         int mid = l + r >> 1;
      |                   ~~^~~
towers.cpp: In lambda function:
towers.cpp:107:13: warning: unused variable 'ans' [-Wunused-variable]
  107 |         int ans = ids.size();
      |             ^~~

• Subtask 1: 0 / 4
• Subtask 2: 0 / 11
• Subtask 3: 0 / 12
• Subtask 4: 0 / 14
• Subtask 5: 0 / 17
• Subtask 6: 0 / 19
• Subtask 7: 0 / 23