Submission #799949

#	Time	Username	Problem	Language	Result	Execution time	Memory
799949		finn__	Fountain Parks (IOI21_parks)	C++17	30 / 100	111 ms	19264 KiB

parks

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

struct fountain
{
    int x, y;
    size_t i;
};

template <size_t N>
struct dsu
{
    int t[N];

    dsu() { memset(t, 255, sizeof t); }

    int repr(int u) { return t[u] < 0 ? u : t[u] = repr(t[u]); }

    bool same_component(int u, int v) { return repr(u) == repr(v); }

    int component_size(int u) { return -t[repr(u)]; }

    void merge(int u, int v)
    {
        u = repr(u), v = repr(v);
        if (u == v)
            return;
        if (t[u] > t[v])
            swap(u, v);
        t[u] += t[v];
        t[v] = u;
    }
};

constexpr size_t N = 200000;

dsu<N> d;
bitset<N> occupied[8];

int construct_roads(vector<int> x, vector<int> y)
{
    size_t const n = x.size();

    vector<fountain> f;
    for (size_t i = 0; i < n; ++i)
        f.push_back({x[i], y[i], i});
    sort(f.begin(), f.end(), [](auto const &a, auto const &b)
         { return a.y == b.y ? a.x < b.x : a.y < b.y; });

    vector<int> u, v, a, b;

    auto add_edge = [&](size_t i, size_t j)
    {
        u.push_back(i);
        v.push_back(j);
        d.merge(i, j);
    };

    auto add_bench = [&](size_t x, size_t y)
    {
        assert(!occupied[x][y]);
        a.push_back(x);
        b.push_back(y);
        occupied[x][y] = 1;
    };

    for (size_t i = 0; i < n;)
    {
        size_t j = i;
        while (j < n && f[j].y == f[i].y)
            ++j;

        if (j - i >= 2 && f[i + 1].x - f[i].x == 2 && !d.same_component(f[i].i, f[i + 1].i))
        {
            add_edge(f[i].i, f[i + 1].i);
            if (!occupied[f[i].x + 1][f[i].y - 1])
                add_bench(f[i].x + 1, f[i].y - 1);
            else
                add_bench(f[i].x + 1, f[i].y + 1);
        }
        if (j - i >= 3 && f[i + 2].x - f[i + 1].x == 2 && !d.same_component(f[i + 1].i, f[i + 2].i))
        {
            add_edge(f[i + 1].i, f[i + 2].i);
            if (!occupied[f[i + 1].x + 1][f[i + 1].y - 1])
                add_bench(f[i + 1].x + 1, f[i + 1].y - 1);
            else
                add_bench(f[i + 1].x + 1, f[i + 1].y + 1);
        }

        if (j < n && f[j].y == f[i].y + 2)
        {
            size_t k = j;
            while (i < j && k < n && f[k].y == f[j].y)
            {
                if (f[i].x < f[k].x)
                    ++i;
                else if (f[i].x > f[k].x)
                    ++k;
                else
                {
                    add_edge(f[i].i, f[k].i);
                    if (f[i].x == 2)
                        add_bench(f[i].x - 1, f[i].y + 1);
                    else if (f[i].x == 6)
                        add_bench(f[i].x + 1, f[i].y + 1);
                    else
                    {
                        if (!occupied[f[i].x - 1][f[i].y + 1])
                            add_bench(f[i].x - 1, f[i].y + 1);
                        else
                            add_bench(f[i].x + 1, f[i].y + 1);
                    }
                    ++i;
                    ++k;
                }
            }
        }

        i = j;
    }

    if (d.component_size(0) != n)
        return 0;
    build(u, v, a, b);
    return 1;
}

Compilation message (stderr)

parks.cpp: In function 'int construct_roads(std::vector<int>, std::vector<int>)':
parks.cpp:123:29: warning: comparison of integer expressions of different signedness: 'int' and 'const size_t' {aka 'const long unsigned int'} [-Wsign-compare]
  123 |     if (d.component_size(0) != n)
      |         ~~~~~~~~~~~~~~~~~~~~^~~~

• Subtask 1: 5 / 5
• Subtask 2: 10 / 10
• Subtask 3: 15 / 15
• Subtask 4: 0 / 20
• Subtask 5: 0 / 20
• Subtask 6: 0 / 30