Submission #797135

#	Time	Username	Problem	Language	Result	Execution time	Memory
797135		t6twotwo	Fountain Parks (IOI21_parks)	C++17	70 / 100	675 ms	94136 KiB

parks

#include "parks.h"
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
struct dsu {
    int n;
    vector<int> p, s;
    dsu(int n) : n(n), p(n), s(n, 1) {
        iota(p.begin(), p.end(), 0);
    }
    int find(int x) {
        return x == p[x] ? x : p[x] = find(p[x]);
    }
    int size(int x) {
        return s[find(x)];
    }
    bool same(int x, int y) {
        return find(x) == find(y);
    }
    bool unite(int x, int y) {
        x = find(x);
        y = find(y);
        if (x == y) {
            return 0;
        }
        if (s[x] > s[y]) {
            swap(x, y);
        }
        p[x] = y;
        s[y] += s[x];
        return 1;
    }
};
constexpr int A = 200000;
struct road {
    int a, b, c;
    pair<int, int> t[2];
    road() {
    }
    road(int A, int B, int C, pair<int, int> U, pair<int, int> V) {
        a = A, b = B, c = C, t[0] = U, t[1] = V;
    }
};
int construct_roads(vector<int> X, vector<int> Y) {
    int N = X.size();
    if (*max_element(X.begin(), X.end()) <= 6) {
        vector f(7, vector(A + 3, -1));
        for (int i = 0; i < N; i++) {
            f[X[i]][Y[i]] = i;
        }
        dsu uf(N);
        vector<int> u, v, a, b, m(A + 1, -1), l(A + 1, -1), r(A + 1, -1);
        for (int y = 2; y <= A; y += 2) {
            for (int x = 2; x <= 6; x += 2) {
                if (f[x][y] != -1 && f[x][y + 2] != -1) {
                    if (x == 4) {
                        m[y + 1] = u.size();
                    }
                    u.push_back(f[x][y]);
                    v.push_back(f[x][y + 2]);
                    a.push_back(x == 2 ? 1 : 7);
                    b.push_back(y + 1);
                    uf.unite(f[x][y], f[x][y + 2]);
                }
                if (x != 6 && f[x][y] != -1 && f[x + 2][y] != -1) {
                    if (x == 2 && l[y - 2] == -1) {
                        l[y] = u.size();
                        u.push_back(f[x][y]);
                        v.push_back(f[x + 2][y]);
                        a.push_back(3);
                        b.push_back(-1);
                        uf.unite(f[x][y], f[x + 2][y]);
                    }
                    if (x == 4 && r[y - 2] == -1) {
                        r[y] = u.size();
                        u.push_back(f[x][y]);
                        v.push_back(f[x + 2][y]);
                        a.push_back(5);
                        b.push_back(-1);
                        uf.unite(f[x][y], f[x + 2][y]);
                    }
                }
            }
        }
        if (uf.size(0) != N) {
            return 0;
        }
        vector<int> q(A, -1), s(A, -1), t(A, -1);
        for (int i = 1; i <= A; i++) {
            if (i % 2 == 1 && m[i] != -1) {
                if (s[i - 1] != 1) {
                    a[m[i]] = 3;
                    q[i] = 0;
                } else {
                    assert(t[i - 1] != 1);
                    a[m[i]] = 5;
                    q[i] = 1;
                }
            }
            if (i % 2 == 0) {
                if (l[i] != -1) {
                    if (q[i - 1] == 0) {
                        b[l[i]] = i + 1;
                        s[i] = 1;
                    } else {
                        b[l[i]] = i - 1;
                        s[i] = 0;
                    }
                }
                if (r[i] != -1) {
                    if (q[i - 1] == 1) {
                        b[r[i]] = i + 1;
                        t[i] = 1;
                    } else {
                        b[r[i]] = i - 1;
                        t[i] = 0;
                    }
                }
            }
        }
        build(u, v, a, b);
        return 1;
    }
    map<int, int> mp[A + 1];
    for (int i = 0; i < N; i++) {
        mp[X[i]][Y[i]] = i;
    }
    dsu uf(N);
    vector<road> roads;
    for (int i = 0; i < N; i++) {
        for (int dx = -2; dx <= 2; dx += 4) {
            if (X[i] + dx < 0 || X[i] + dx > A) {
                continue;
            }
            if (mp[X[i] + dx].count(Y[i])) {
                int j = mp[X[i] + dx][Y[i]];
                if (!uf.same(i, j)) {
                    uf.unite(i, j);
                    roads.push_back(road(i, j, -1, pair{X[i] + dx / 2, Y[i] + 1}, pair{X[i] + dx / 2, Y[i] - 1}));
                }
            }
        }
        for (int dy = -2; dy <= 2; dy += 4) {
            if (Y[i] + dy < 0 || Y[i] + dy > A) {
                continue;
            }
            if (mp[X[i]].count(Y[i] + dy)) {
                int j = mp[X[i]][Y[i] + dy];
                if (!uf.same(i, j)) {
                    uf.unite(i, j);
                    roads.push_back(road(i, j, -1, pair{X[i] - 1, Y[i] + dy / 2}, pair{X[i] + 1, Y[i] + dy / 2}));
                }
            }
        }
    }
    if (uf.size(0) != N) {
        return 0;
    }
    map<int, vector<pair<int, int>>> f[A + 3];
    for (int z = 0; z < roads.size(); z++) {
        auto r = roads[z];
        for (int i = 0; i < 2; i++) {
            auto [x, y] = r.t[i];
            f[x][y].emplace_back(z, i);
        }
    }
    for (int z = 0; z < roads.size(); z++) {
        if (roads[z].c != -1) {
            continue;
        }
        for (int d = 0; d < 2; d++) {
            bool ok = 1;
            vector<int> q;
            roads[z].c = d;
            q.push_back(z);
            for (int i = 0; ok && i < q.size(); i++) {
                int u = q[i];
                int color = roads[u].c;
                auto [x, y] = roads[u].t[color];
                for (auto [v, w] : f[x][y]) {
                    if (roads[v].c == -1) {
                        roads[v].c = 1 - w;
                        q.push_back(v);
                    }
                    if (v != u && roads[v].c == w) {
                        ok = 0;
                        break;
                    }
                }
            }
            if (ok) {
                break;
            }
            if (!ok) {
                if (d == 1) {
                    return 0;
                }
                for (int x : q) {
                    roads[x].c = -1;
                }
            }
        }
    }
    vector<int> u, v, a, b;
    for (auto r : roads) {
        u.push_back(r.a);
        v.push_back(r.b);
        auto [x, y] = r.t[r.c];
        a.push_back(x);
        b.push_back(y);
    }
    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:160:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<road>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  160 |     for (int z = 0; z < roads.size(); z++) {
      |                     ~~^~~~~~~~~~~~~~
parks.cpp:167:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<road>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  167 |     for (int z = 0; z < roads.size(); z++) {
      |                     ~~^~~~~~~~~~~~~~
parks.cpp:176:37: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  176 |             for (int i = 0; ok && i < q.size(); i++) {
      |                                   ~~^~~~~~~~~~

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