Submission #787173

#	Time	Username	Problem	Language	Result	Execution time	Memory
787173		MilosMilutinovic	Radio Towers (IOI22_towers)	C++17	0 / 100	604 ms	33840 KiB

towers

#include "towers.h"
#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 10;
const int L = 22;
int n, a[N], pl[N], pr[N], ord[N];
bool cmp(int i, int j) { return a[i] < a[j]; }
int mx[N][L], logs[N];
int qmx(int l, int r) {
    if (l > r) return (int) -1e9;
    int k = logs[r - l + 1];
    return max(mx[l][k], mx[r - (1 << k) + 1][k]);
}
void buildST() {
    for (int i = 1; i <= n; i++) mx[i][0] = a[i];
    for (int i = 2; i <= n; i++) logs[i] = logs[i >> 1] + 1;
    for (int j = 1; j < L; j++)
        for (int i = 1; i + (1 << j) <= n + 1; i++)
            mx[i][j] = max(mx[i][j - 1], mx[i + (1 << (j - 1))][j - 1]);
}
const int M = N * L;
int tsz, ls[M], rs[M], sum[M];
void modify(int& v, int p, int tl, int tr, int i, int x) {
    v = ++tsz;
    ls[v] = ls[p];
    rs[v] = rs[p];
    sum[v] = sum[p] + x;
    if (tl == tr) {
        return;
    }
    int mid = tl + tr >> 1;
    if (i <= mid) {
        modify(ls[v], ls[p], tl, mid, i, x);
    } else {
        modify(rs[v], rs[p], mid + 1, tr, i, x);
    }
}
int query(int v, int tl, int tr, int ql, int qr) {
    if (tl > tr || tl > qr || tr < ql) {
        return 0;
    }
    if (ql <= tl && tr <= qr) {
        return sum[v];
    }
    int mid = tl + tr >> 1;
    return query(ls[v], tl, mid, ql, qr) + query(rs[v], mid + 1, tr, ql, qr);
}
int find_first(int v, int tl, int tr, int p) {
    if (tr < p || !sum[v]) {
        return n + 1;
    }
    if (tl == tr) {
        return sum[v] > 0 ? tl : n + 1;
    }
    int mid = tl + tr >> 1;
    int ans_l = find_first(ls[v], tl, mid, p);
    if (ans_l == n + 1)
        return find_first(rs[v], mid + 1, tr, p);
    else
        return ans_l;
}
int find_last(int v, int tl, int tr, int p) {
    if (tl > p || !sum[v]) {
        return 0;
    }
    if (tl == tr) {
        return sum[v] > 0 ? tl : 0;
    }
    int mid = tl + tr >> 1;
    int ans_r = find_last(ls[v], mid + 1, tr, p);
    if (ans_r == 0)
        return find_last(ls[v], tl, mid, p);
    else
        return ans_r;
}
vector<pair<int, int>> qs;
vector<int> roots(1, 0);
void init(int N, vector<int> H) {
    n = N;
    for (int i = 1; i <= n; i++) {
        a[i] = H[i - 1];
    }
    vector <int> stk;
    for (int i = 1; i <= n; i++) {
        while (!stk.empty() && a[stk.back()] > a[i]) stk.pop_back();
        pl[i] = (stk.empty() ? -1 : stk.back());
        stk.push_back(i);
    }
    stk.clear();
    for (int i = n; i >= 1; i--) {
        while (!stk.empty() && a[stk.back()] > a[i]) stk.pop_back();
        pr[i] = (stk.empty() ? -1 : stk.back());
        stk.push_back(i);
    }
    buildST();
    for (int i = 1; i <= n; i++) ord[i] = i;
    sort(ord + 1, ord + n + 1, cmp);
    for (int _i = 2; _i <= n; _i++) {
        int i = ord[_i];
        int D = 1.001e9;
        if (pl[i] != -1) D = min(D, qmx(pl[i] + 1, i) - a[i]);
        if (pr[i] != -1) D = min(D, qmx(i, pr[i] - 1) - a[i]);
        qs.emplace_back(D, i);
    }
    roots.push_back(0);
    int sz = (int) qs.size();
    for (int i = sz - 1; i >= 0; i--) {
        int prv = (int) roots.size();
        roots.push_back(0);
        modify(roots.back(), prv, 1, n, qs[i].second, 1);
    }
    reverse(roots.begin(), roots.end());
}
int max_towers(int L, int R, int D) {
    if (L == R) {
        return 1;
    }
    ++L; ++R;
    int p = (int) (qs.end() - lower_bound(qs.begin(), qs.end(), make_pair(D, -1)));
    int ans = query(roots[p], 1, n, L, R);
    int l = find_first(roots[p], 1, n, L);
    int r = find_last(roots[p], 1, n, R);
    return ans;
}

/*
7 1
10 20 60 40 50 30 70
0 6 17
*/

Compilation message (stderr)

towers.cpp: In function 'void modify(int&, int, int, int, int, int)':
towers.cpp:31:18: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   31 |     int mid = tl + tr >> 1;
      |               ~~~^~~~
towers.cpp: In function 'int query(int, int, int, int, int)':
towers.cpp:45:18: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   45 |     int mid = tl + tr >> 1;
      |               ~~~^~~~
towers.cpp: In function 'int find_first(int, int, int, int)':
towers.cpp:55:18: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   55 |     int mid = tl + tr >> 1;
      |               ~~~^~~~
towers.cpp: In function 'int find_last(int, int, int, int)':
towers.cpp:69:18: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   69 |     int mid = tl + tr >> 1;
      |               ~~~^~~~
towers.cpp: In function 'int max_towers(int, int, int)':
towers.cpp:121:9: warning: unused variable 'l' [-Wunused-variable]
  121 |     int l = find_first(roots[p], 1, n, L);
      |         ^
towers.cpp:122:9: warning: unused variable 'r' [-Wunused-variable]
  122 |     int r = find_last(roots[p], 1, n, R);
      |         ^

• 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