Submission #759516

#	Time	Username	Problem	Language	Result	Execution time	Memory
759516		drdilyor	Fountain Parks (IOI21_parks)	C++17	5 / 100	377 ms	24480 KiB

parks

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

struct DSU {
    int n;
    vector<int> parent;
    vector<int> size;

    DSU(int n) : n(n), parent(n), size(n, 1) {
        iota(parent.begin(), parent.end(), 0);
    }

    int get(int i) {
        return parent[i] == i ? i : parent[i] = get(parent[i]);
    }

    void merge(int v, int u) {
        v = get(v);
        u = get(u);
        if (u == v) return;
        if (size[v] < size[u]) swap(v, u);
        parent[u] = v;
        size[v] += size[u];
    }
};


int construct_roads(std::vector<int> x, std::vector<int> y) {
    if (x.size() == 1) {
        build({}, {}, {}, {});
        return 1;
    }

    int n = x.size();

    std::vector<int> u, v, a, b;
    vector<pair<int,int>> d;
    map<pair<int,int>, int> ft;
    for (int i = 0; i < n;i ++)
        ft[{x[i], y[i]}] = i;
    vector<tuple<int,int,int>> road;
    set<pair<int,int>> bench;

    for (int i = 0; i < n; i++) {
        for (auto [dx, dy] : {pair{0, -2}, {0, +2}, {-2, 0}, {+2, 0}}) {
            pair pos{x[i]+dx, y[i]+dy};
            if (!ft.count(pos)) continue;
            int j = ft[pos];
            if (j < i) continue;
            u.push_back(i);
            v.push_back(j);
            road.push_back({x[i]+dx/2, y[i]+dy/2, u.size()-1});
            d.push_back({dx, dy});
        }
    }
    a.resize(u.size());
    b.resize(u.size());

    sort(road.begin(), road.end());
    for (auto [_x, _y, ri] : road) {
        auto [dx, dy] = d[ri];
        int i = u[ri], j = v[ri];
        vector<pair<int,int>> pos_bench;
        if (dx) {
            pos_bench = {{x[i]+dx/2, y[i]-1}, {x[i]+dx/2, y[i]+1}};
        } else {
            pos_bench = {{x[i]-1, y[i]+dy/2}, {x[i]+1, y[i]+dy/2}};
        }
        bool done = 0;
        for (auto pos : pos_bench) {
            if (bench.count(pos) == 0) {
                done = 1;
                a[ri] = pos.first;
                b[ri] = pos.second;
                break;
            }
            bench.insert(pos);
        }
        if (!done) return 0;
    }

    DSU cc(n);
    for (int i = 0; i < (int)u.size(); i++) {
        cc.merge(u[i], v[i]);
    }
    if (cc.size[cc.get(0)] != n || (int)u.size() != n-1) 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:63:24: warning: unused variable 'j' [-Wunused-variable]
   63 |         int i = u[ri], j = v[ri];
      |                        ^

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