Submission #940764

#	Time	Username	Problem	Language	Result	Execution time	Memory
940764		Trisanu_Das	Radio Towers (IOI22_towers)	C++17	56 / 100	720 ms	14560 KiB

towers

#include "towers.h"
 
#include <bits/stdc++.h>
using namespace std;
 
vector<int> h;
int n;
void init(int N, vector<int> H) {
    n = N;
    h = H;
}
 
bool processed = false;
vector<int> nxt, dow;
vector<vector<int>> jump;
int max_towers(int l, int r, int D) {
    if (!processed) {
        processed = true;
        deque<pair<int, int>> st;
        nxt.assign(n + 1, n);
        dow.assign(n + 1, n);
        for (int i = n - 1; i >= 0; i--) {
            while (!st.empty() && h[st.front().second] <= h[i]) st.pop_front();
            st.push_front({h[i], i});
            auto p = lower_bound(st.begin(), st.end(), pair{h[i] + D, -1});
            if (p != st.end()) {
                nxt[i] = p->second;
            }
        }
        for (int i = n - 2; i >= 0; i--) {
            nxt[i] = min(nxt[i], nxt[i + 1]);
        }
        st.clear();
        for (int i = n - 1; i >= 0; i--) {
            while (!st.empty() && h[st.back().second] >= h[i]) st.pop_back();
            st.push_back({h[i], i});
            auto p = lower_bound(st.begin(), st.end(), pair{h[i] - D + 1, -1});
            if (p != st.begin()) {
                p--;
                dow[i] = p->second;
            }
        }
        for (int i = n - 2; i >= 0; i--) {
            dow[i] = min(dow[i], dow[i + 1]);
        }
        jump.assign(n + 1, vector<int>(20, n));
        for (int i = 0; i < n; i++) {
            jump[i][0] = nxt[i];
            jump[i][1] = dow[nxt[i]];
        }
        for (int j = 2; j < 20; j++) {
            for (int i = 0; i < n; i++) {
                jump[i][j] = jump[jump[i][j - 1]][j - 1];
            }
        }
    }
    int p = l;
    int s = 0;
    for (int i = 19; i >= 1; i--) {
        if (jump[p][i] <= r) {
            p = jump[p][i];
            s += 1 << i;
        }
    }
    return s / 2 + 1;
}

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