Submission #1068769

#	Time	Username	Problem	Language	Result	Execution time	Memory
1068769		Boas	Fountain Parks (IOI21_parks)	C++17	70 / 100	310 ms	69692 KiB

parks

#include "parks.h"

#include <bits/stdc++.h>
using namespace std;
typedef vector<int> vi;
typedef long long ll;
typedef vector<signed> vi32;
typedef vector<bool> vb;
typedef vector<vi> vvi;
typedef unordered_set<ll> si;
typedef pair<int, int> ii;
typedef tuple<int, int, int> iii;
typedef vector<ii> vii;
typedef set<iii> siii;
// typedef unordered_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}};

vector<si> benchPoints(4); // neighbour count

ll MX = 200'002;

ll toInt(ii p)
{
    auto [b, c] = p;
    return MX * b + c;
}

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

int construct_roads(vi xs, vi ys)
{
    unordered_map<ll, int> fountains;
    unordered_map<ll, int> roads;
    // unordered_set<ii> gotBench;
    int n = sz(xs);
    loop(n, i)
    {
        fountains[toInt({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(toInt(pos)))
            {
                int j = fountains[toInt(pos)];
                if (vis[j])
                    continue;
                if (dx != 0)
                {
                    roads[toInt({x + dx / 2, y})] = sz(u);
                    addNeighbour(x + dx / 2, y + 1);
                    addNeighbour(x + dx / 2, y - 1);
                }
                else
                {
                    roads[toInt({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++)
    {
        ll x, y;
        for (int i = 1; i <= 3; i++)
        {
            if (!benchPoints[i].empty())
            {
                ll pr = *benchPoints[i].begin();
                x = pr / MX, y = pr % MX;
                benchPoints[i].erase(benchPoints[i].begin());
                break;
            }
        }
        ii loc;
        if (roads.count(toInt({x + 1, y})))
        {
            loc = {x + 1, y};
            addNeighbour(x + 2, y, -1);
        }
        else if (roads.count(toInt({x - 1, y})))
        {
            loc = {x - 1, y};
            addNeighbour(x - 2, y, -1);
        }
        else if (roads.count(toInt({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[toInt(loc)];
        roads.erase(toInt(loc));
        a[ix] = x;
        b[ix] = y;
    }
    build(u, v, a, b);
    return 1;
}

Compilation message (stderr)

parks.cpp: In function 'int construct_roads(vi, vi)':
parks.cpp:147:15: warning: 'x' may be used uninitialized in this function [-Wmaybe-uninitialized]
  147 |         a[ix] = x;

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