Submission #1240601

#	Time	Username	Problem	Language	Result	Execution time	Memory
1240601		trimkus	Fountain Parks (IOI21_parks)	C++20	5 / 100	220 ms	38156 KiB

parks

#include "parks.h"
#include <bits/stdc++.h>

using namespace std;

struct DSU {
    vector<int> e;
    DSU (int n) {
        e = vector<int>(n, -1);
    }
    int get(int x) {
        return e[x] < 0 ? x : e[x] = get(e[x]);
    }
    void unite(int x, int y) {
        x = get(x);
        y = get(y);
        if (x == y) return;
        if (e[x] > e[y]) swap(x, y);
        e[x] += e[y];
        e[y] = x;
    }
};

int construct_roads(std::vector<int> x, std::vector<int> y) {
    if (x.size() == 1) {
	    build({}, {}, {}, {});
        return 1;
    }
    vector<array<int, 3>> st;
    int N = x.size();
    for (int i = 0; i < N; ++i) {
        st.push_back({x[i], y[i], i});
    }
    sort(begin(st), end(st));
    vector<array<int, 2>> con;
    for (int i = 1; i < N; ++i) {
        if (st[i][0] == st[i - 1][0] && st[i][1] - st[i - 1][1] == 2) {
            con.push_back({st[i][2], st[i - 1][2]});
        }
    }
    st.clear();
    for (int i = 0; i < N; ++i) {
        st.push_back({y[i], x[i], i});
    }
    sort(begin(st), end(st));
    for (int i = 1; i < N; ++i) {
        if (st[i][0] == st[i - 1][0] && st[i][1] - st[i - 1][1] == 2) {
            con.push_back({st[i][2], st[i - 1][2]});
        }
    }
    for (int i = 0; i < (int)con.size(); ++i) {
        if (con[i][0] > con[i][1]) swap(con[i][0], con[i][1]);
    }
    sort(begin(con), end(con));
    con.erase(unique(begin(con), end(con)), end(con));
    DSU dsu(N);
    for (auto& [x, y] : con) {
        dsu.unite(x, y);
    }
    if (-dsu.e[dsu.get(0)] != N) return 0;
    vector<vector<int>> adj(N);
    for (auto& [i, j] : con) {
        adj[i].push_back(j);
        adj[j].push_back(i);
    }
    int M = con.size();
    set<array<int, 2>> vis_edge, vis_cord;
    queue<int> q;
    for (int i = 0; i < N; ++i) {
        if (adj[i].size() == 3) q.push(i);
        assert(adj[i].size() <= 3);
    }
    vector<int> v, u, a, b;
    auto ok = [&](int X, int Y, vector<array<int, 2>>& now) -> bool {
        for (auto [f, g] : now) {
            if (X == f && g == Y) return false;
        }
        return !vis_cord.count({X, Y});
    };
    auto dfs = [&](auto& dfs, int i, int idx, vector<array<int, 2>>& now) -> bool {
        // cerr << idx << " -> ";
        // cerr << adj[i].size() << "\n";
        if (idx == adj[i].size()) return true;
        
        int j = adj[i][idx];
        if (x[i] == x[j]) {
            int ny = min(y[i], y[j]) + 1;
            int nx = x[i] + 1;
            if (ok(nx, ny, now)) {
                now.push_back({nx, ny});
                if (dfs(dfs, i, idx + 1, now)) {
                    // cerr << "Done!\n";
                    return true;
                
                }
                now.pop_back();
            }
            nx = x[i] - 1;
            if (ok(nx, ny, now)) {
                now.push_back({nx, ny});
                if (dfs(dfs, i, idx + 1, now)) return true;
                now.pop_back();
            }
            assert(false);
        } else {    
            assert(y[i] == y[j]);
            int nx = min(x[i], x[j]) + 1;
            int ny = y[i] + 1;
            if (ok(nx, ny, now)) {
                now.push_back({nx, ny});
                if (dfs(dfs, i, idx + 1, now)) return true;
                now.pop_back();
            }
            ny = y[i] - 1;
            if (ok(nx, ny, now)) {
                now.push_back({nx, ny});
                if (dfs(dfs, i, idx + 1, now)) return true;
                now.pop_back();
            }
            assert(false);
        }
        return false;
    };
    while (q.size()) {
        int i = q.front();
        q.pop();
        // cerr << i << endl;
        bool can = true;
        for (auto& j : adj[i]) {
            if (vis_edge.count({min(i, j), max(i, j)})) {
                can = false;
            }
        }
        if (!can) continue;
        vector<array<int, 2>> now;
        assert(dfs(dfs, i, 0, now));
        // cerr << "Here!\n";
        for (int _ = 0; _ < 3; ++_) {
            int j = adj[i][_];
            u.push_back(i);
            v.push_back(j);
            a.push_back(now[_][0]);
            b.push_back(now[_][1]);
        }
        for (auto& [X, Y] : now) {
            vis_cord.insert({X, Y});
        }
        for (auto& j : adj[i]) {
            vis_edge.insert({min(i, j), max(i, j)});
        }
    }
    for (int it = 0; it < M; ++it) {
        int i = con[it][0];
        int j = con[it][1];
        if (i > j) swap(i, j);
        if (vis_edge.count({i, j})) continue;
        v.push_back(i);
        u.push_back(j);
        if (x[i] == x[j]) {
            int ny = min(y[i], y[j]) + 1;
            b.push_back(ny);
            int nx = x[i] + 1;
            if (!vis_cord.count({nx, ny})) {
                a.push_back(nx);
            } else {
                nx = x[i] - 1;
                assert(!vis_cord.count({nx, ny}));
                a.push_back(nx);
            }
            vis_cord.insert({nx, ny});
        } else {    
            int nx = min(x[i], x[j]) + 1;
            a.push_back(nx);
            int ny = y[i] + 1;
            if (!vis_cord.count({nx, ny})) {
                b.push_back(ny);
            } else {
                ny = y[i] - 1;
                assert(!vis_cord.count({nx, ny}));
                b.push_back(ny);
            }
            vis_cord.insert({nx, ny});
        }
    }
    build(v, u, a, b);
    return 1;
}

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