Submission #613986

#	Time	Username	Problem	Language	Result	Execution time	Memory
613986		dxz05	Fountain Parks (IOI21_parks)	C++17	30 / 100	434 ms	55384 KiB

parks

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

using namespace std;
#define MP make_pair
#define all(x) (x).begin(), (x).end()

struct dsu {
    vector<int> p, sz;
    dsu(int n) {
        p.assign(n, 0);
        sz.assign(n, 1);
        iota(p.begin(), p.end(), 0);
    }

    int find(int x) {
        return (x == p[x] ? x : p[x] = find(p[x]));
    }

    bool unite(int x, int y) {
        x = find(x);
        y = find(y);
        if (x == y) return false;
        if (sz[x] > sz[y]) swap(x, y);
        p[x] = y;
        sz[y] += sz[x];
        return true;
    }
};

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

    map<pair<int, int>, int> id;
    for (int i = 0; i < n; i++) id[MP(x[i], y[i])] = i;

    vector<int> U, V, A, B;
    
    vector<int> perm(n);
    iota(all(perm), 0);
    sort(all(perm), [&](int i, int j){
        return MP(x[i], y[i]) < MP(x[j], y[j]);
    });

    dsu d(n);
    for (int i : perm){
        if (id.find(MP(x[i], y[i] + 2)) == id.end()) continue;
        int j = id[MP(x[i], y[i] + 2)];
        if (d.unite(i, j)){
            U.push_back(i);
            V.push_back(j);
        }
    }

    for (int i : perm) {
        if (id.find(MP(x[i] + 2, y[i])) == id.end()) continue;
        int j = id[MP(x[i] + 2, y[i])];
        if (d.unite(i, j)) {
            U.push_back(i);
            V.push_back(j);
        }
    }

    if (U.size() != n - 1) return 0;

    A.resize(n - 1);
    B.resize(n - 1);

    set<pair<int, int>> benches;

    int k = 0;
    for (int it = 0; it < n - 1; it++){
        int i = U[it], j = V[it];
        if (x[i] == x[j]){
            B[it] = (y[i] + y[j]) / 2;
            if (x[i] == 2 || x[i] == 6){
                A[it] = (x[i] == 2 ? 1 : 7);
            } else {
                if (k){
                    A[it] = x[i] - 1;
                } else {
                    A[it] = x[i] + 1;
                }
                k ^= 1;
            }
            benches.insert(MP(A[it], B[it]));
        }
    }

    for (int it = 0; it < n - 1; it++) {
        int i = U[it], j = V[it];
        if (y[i] == y[j]) {
            int xx = (x[i] + x[j]) / 2;
            A[it] = xx;
            if (!benches.count(MP(xx, y[i] + 1))){
                B[it] = y[i] + 1;
            } else 
            if (!benches.count(MP(xx, y[i] - 1))){
                B[it] = y[i] - 1;
            } else {
                assert(false);
            }
            benches.insert(MP(A[it], B[it]));
        }
    }

    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:68:18: warning: comparison of integer expressions of different signedness: 'std::vector<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   68 |     if (U.size() != n - 1) return 0;
      |         ~~~~~~~~~^~~~~~~~

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