Submission #1068716

#	Time	Username	Problem	Language	Result	Execution time	Memory
1068716		Boas	Fountain Parks (IOI21_parks)	C++17	70 / 100	3533 ms	90020 KiB

parks

#include "parks.h"

#include <bits/stdc++.h>
using namespace std;
typedef vector<int> vi;
typedef vector<signed> vi32;
typedef vector<bool> vb;
typedef vector<vi> vvi;
typedef set<int> si;
typedef pair<int, int> ii;
typedef tuple<int, int, int> iii;
typedef vector<ii> vii;
typedef set<iii> siii;
typedef set<ii> sii;
typedef vector<vii> vvii;
#define pb push_back
#define loop(x, i) for (int i = 0; i < x; i++)
#define ALL(x) begin(x), end(x)
#define sz(x) (int)x.size()

vii adj = {{-2, 0}, {2, 0}, {0, 2}, {0, -2}};

siii benchPoints; // neighbour count

void addNeighbour(int x, int y, int dif = 1)
{
    if (benchPoints.count({1, x, y}))
    {
        benchPoints.erase({1, x, y});
        if (dif == 1)
        {
            benchPoints.insert({2, x, y});
        }
    }
    else if (benchPoints.count({2, x, y}))
    {
        benchPoints.erase({2, x, y});
        benchPoints.insert({2 + dif, x, y});
    }
    else if (benchPoints.count({3, x, y}))
    {
        benchPoints.erase({3, x, y});
        if (dif == 1)
            throw;
        benchPoints.insert({2, x, y});
    }
    else if (dif == 1)
    {
        benchPoints.insert({1, x, y});
    }
}

int construct_roads(vi xs, vi ys)
{
    map<ii, int> fountains;
    map<ii, int> roads;
    // set<ii> gotBench;
    int n = sz(xs);
    loop(n, i)
    {
        fountains[{xs[i], ys[i]}] = i;
    }
    vb vis(n);
    vi u, v, a, b;
    a = b = vi(n - 1);
    int visCnt = 1;
    auto dfs = [&](auto &&self, int i) -> void
    {
        int x = xs[i], y = ys[i];
        for (const auto &[dx, dy] : adj)
        {
            ii pos = {x + dx, y + dy};
            if (fountains.count(pos))
            {
                int j = fountains[pos];
                if (vis[j])
                    continue;
                if (dx != 0)
                {
                    roads[{x + dx / 2, y}] = sz(u);
                    addNeighbour(x + dx / 2, y + 1);
                    addNeighbour(x + dx / 2, y - 1);
                }
                else
                {
                    roads[{x, y + dy / 2}] = sz(u);
                    addNeighbour(x + 1, y + dy / 2);
                    addNeighbour(x - 1, y + dy / 2);
                }
                u.pb(i);
                v.pb(j);
                vis[j] = 1;
                visCnt++;
                self(self, j);
            }
        }
    };
    vis[0] = 1;
    dfs(dfs, 0);
    if (visCnt != n)
        return 0;
    for (int benchesBuilt = 0; benchesBuilt < n - 1; benchesBuilt++)
    {
        auto [cnt, x, y] = *benchPoints.begin();
        benchPoints.erase(benchPoints.begin());
        ii loc;
        if (roads.count({x + 1, y}))
        {
            loc = {x + 1, y};
            addNeighbour(x + 2, y, -1);
        }
        else if (roads.count({x - 1, y}))
        {
            loc = {x - 1, y};
            addNeighbour(x - 2, y, -1);
        }
        else if (roads.count({x, y + 1}))
        {
            loc = {x, y + 1};
            addNeighbour(x, y + 2, -1);
        }
        else
        {
            loc = {x, y - 1};
            addNeighbour(x, y - 2, -1);
        }
        int ix = roads[loc];
        roads.erase(loc);
        a[ix] = x;
        b[ix] = y;
    }
    build(u, v, a, b);
    return 1;
}

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