Submission #817078

#	Time	Username	Problem	Language	Result	Execution time	Memory
817078		finn__	Radio Towers (IOI22_towers)	C++17	4 / 100	4019 ms	17488 KiB

towers

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

template <typename T, size_t L>
struct segtree_max
{
    T t[L << 1];

    void update(size_t i, T x)
    {
        i += L;
        t[i] = max(t[i], x);
        while (i >>= 1)
            t[i] = max(t[i << 1], t[i << 1 | 1]);
    }

    T range_max(size_t i, size_t j)
    {
        i += L, j += L;
        T x = numeric_limits<T>::min();

        while (i <= j)
        {
            if (i & 1)
                x = max(x, t[i++]);
            if (!(j & 1))
                x = max(x, t[j--]);
            i >>= 1;
            j >>= 1;
        }

        return x;
    }

    void reset() { memset(t, 0, sizeof t); }
};

template <typename T, size_t L>
struct fenwick_tree
{
    T t[L];

    void update(int64_t i, T x)
    {
        ++i;
        while (i <= L)
            t[i - 1] += x, i += i & -i;
    }

    T range_sum(int64_t i, int64_t j)
    {
        ++j;
        T x = 0;
        while (j)
            x += t[j - 1], j -= j & -j;
        while (i)
            x -= t[i - 1], i -= i & -i;
        return x;
    }
};

constexpr size_t N = 100000;

bool subtask1;
int h[N], coords[3 * N];
size_t n, peak_pos;

segtree_max<int64_t, 1 << 19> towers, intermediate;
fenwick_tree<int, N> valleys;

void init(int n_, vector<int> h_)
{
    n = n_;
    copy(h_.begin(), h_.end(), h);
    bool increasing = 1;
    subtask1 = 1;
    for (size_t i = 0; i + 1 < n; ++i)
    {
        if (h[i] < h[i + 1] && !increasing)
        {
            subtask1 = 0;
            break;
        }
        if (h[i] > h[i + 1])
            increasing = 0;
    }

    if (subtask1)
    {
        while (peak_pos + 1 < n && h[peak_pos + 1] > h[peak_pos])
            ++peak_pos;
        return;
    }

    for (size_t i = 0; i < n; ++i)
        if ((!i || h[i - 1] > h[i]) && (i + 1 == n || h[i + 1] > h[i]))
            valleys.update(i, 1);
}

size_t ind(int64_t coord) { return lower_bound(coords, coords + 3 * n, coord) - coords; }

int max_towers(int l, int r, int d)
{
    if (subtask1)
    {
        if (l >= peak_pos || r <= peak_pos)
            return 1;
        return (h[peak_pos] >= h[l] + d && h[peak_pos] >= h[r] + d) + 1;
    }
    else if (d == 1)
    {
        return valleys.range_sum(l, r);
    }
    else
    {
        memcpy(coords, h, sizeof h);
        for (size_t i = 0; i < n; ++i)
            coords[n + i] = coords[i] + d, coords[2 * n + i] = coords[i] - d;
        sort(coords, coords + 3 * n);

        towers.reset();
        intermediate.reset();

        towers.update(ind(h[l]), 1);
        int ans = 1;
        for (size_t i = l + 1; i <= r; ++i)
        {
            // as intermediate
            int64_t v = towers.range_max(0, ind(h[i] - d));
            intermediate.update(ind(h[i]), v);

            // as tower
            v = intermediate.range_max(ind(h[i] + d), 3 * n - 1) + 1;
            towers.update(ind(h[i]), v);
            ans = max<int>(ans, v);
        }

        return ans;
    }
}

Compilation message (stderr)

towers.cpp: In function 'int max_towers(int, int, int)':
towers.cpp:107:15: warning: comparison of integer expressions of different signedness: 'int' and 'size_t' {aka 'long unsigned int'} [-Wsign-compare]
  107 |         if (l >= peak_pos || r <= peak_pos)
      |             ~~^~~~~~~~~~~
towers.cpp:107:32: warning: comparison of integer expressions of different signedness: 'int' and 'size_t' {aka 'long unsigned int'} [-Wsign-compare]
  107 |         if (l >= peak_pos || r <= peak_pos)
      |                              ~~^~~~~~~~~~~
towers.cpp:127:34: warning: comparison of integer expressions of different signedness: 'size_t' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
  127 |         for (size_t i = l + 1; i <= r; ++i)
      |                                ~~^~~~
towers.cpp: In instantiation of 'void fenwick_tree<T, L>::update(int64_t, T) [with T = int; long unsigned int L = 100000; int64_t = long int]':
towers.cpp:98:32:   required from here
towers.cpp:47:18: warning: comparison of integer expressions of different signedness: 'int64_t' {aka 'long int'} and 'long unsigned int' [-Wsign-compare]
   47 |         while (i <= L)
      |                ~~^~~~

• Subtask 1: 4 / 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