Submission #817073

#	Time	Username	Problem	Language	Result	Execution time	Memory
817073		finn__	Radio Towers (IOI22_towers)	C++17	27 / 100	4030 ms	11744 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); }
};

constexpr size_t N = 100000;

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

segtree_max<int64_t, 3 * N> towers, intermediate;

void init(int n_, vector<int> h_)
{
    n = n_;
    copy(h_.begin(), h_.end(), h);
    bool increasing = 1;
    subtask = 1;
    for (size_t i = 0; i + 1 < n; ++i)
    {
        if (h[i] < h[i + 1] && !increasing)
        {
            subtask = 2;
            break;
        }
        if (h[i] > h[i + 1])
            increasing = 0;
    }

    if (subtask == 1)
    {
        while (peak_pos + 1 < n && h[peak_pos + 1] > h[peak_pos])
            ++peak_pos;
        return;
    }
    else
    {
        subtask = 3;
    }
}

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 (subtask == 1)
    {
        if (l >= peak_pos || r <= peak_pos)
            return 1;
        return (h[peak_pos] >= h[l] + d && h[peak_pos] >= h[r] + d) + 1;
    }
    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:81:15: warning: comparison of integer expressions of different signedness: 'int' and 'size_t' {aka 'long unsigned int'} [-Wsign-compare]
   81 |         if (l >= peak_pos || r <= peak_pos)
      |             ~~^~~~~~~~~~~
towers.cpp:81:32: warning: comparison of integer expressions of different signedness: 'int' and 'size_t' {aka 'long unsigned int'} [-Wsign-compare]
   81 |         if (l >= peak_pos || r <= peak_pos)
      |                              ~~^~~~~~~~~~~
towers.cpp:97:34: warning: comparison of integer expressions of different signedness: 'size_t' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   97 |         for (size_t i = l + 1; i <= r; ++i)
      |                                ~~^~~~

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