Submission #1021233

#	Time	Username	Problem	Language	Result	Execution time	Memory
1021233		mdn2002	Fountain Parks (IOI21_parks)	C++17	5 / 100	1253 ms	174800 KiB

parks

/*
Mayoeba Yabureru
*/
#include "parks.h"
#include<bits/stdc++.h>
using namespace std;
static vector<int> _u, _v, _a, _b;

int construct_roads(vector<int> x, vector<int> y) {
    int n = x.size();
    vector<vector<int>> gr(n + 1);
    vector<int> dsu(n + 1);
    x.insert(x.begin(), 0);
    y.insert(y.begin(), 0);
    map<pair<int, int>, int> mp;
    map<pair<int, int>, pair<int, int>> mpp;
    for (int i = 1; i <= n; i ++) {
        mp[{x[i], y[i]}] = i;
        dsu[i] = i;
    }
    vector<int> u, v, a, b;

    map<pair<int, int>, int> taken;

    function<int(int)> fp = [&](int x) {
        if (dsu[x] == x) return x;
        return dsu[x] = fp(dsu[x]);
    };
    for (int i = 1; i <= n; i ++) {
        if (mp[{x[i] + 2, y[i]}]) {
            int fx = fp(i), fy = fp(mp[{x[i] + 2, y[i]}]);
            if (fx != fy) {
                u.push_back(i), v.push_back(mp[{x[i] + 2, y[i]}]);
                gr[i].push_back(mp[{x[i] + 2, y[i]}]);
                gr[mp[{x[i] + 2, y[i]}]].push_back(i);
                dsu[fx] = fy;
            }
        }
        if (mp[{x[i], y[i] + 2}]) {
            int fx = fp(i), fy = fp(mp[{x[i] + 2, y[i]}]);
            if (fx != fy) {
                u.push_back(i), v.push_back(mp[{x[i], y[i] + 2}]);
                gr[i].push_back(mp[{x[i], y[i] + 2}]);
                gr[mp[{x[i], y[i] + 2}]].push_back(i);
                dsu[fx] = fy;
            }
        }
    }

    int num = 0, st = 0;
    vector<int> vis(n + 1);
    for (int i = 1; i <= n; i ++) {
        if (gr[i].size() == 1) {
            st = i;
            break;
        }
    }
    function<void(int)> go = [&] (int v) {
        num ++;
        vis[v] = 1;
        vector nx = {0, 2, 0, -2};
        vector ny = {2, 0, -2, 0};
        int ii = 0;
        for (int i = 0; i < 4; i ++) {
            int u = mp[{x[v] + nx[i], y[v] + ny[i]}];
            if (u == 0) continue;
            if (vis[u]) {
                ii = (i + 1) % 4;
                break;
            }
        }
        int nummmm = 10;
        while (nummmm --) {
            int i = ii;
            ii = (ii + 1) % 4;
            int u = mp[{x[v] + nx[i], y[v] + ny[i]}];
            if (u == 0 || vis[u]) continue;
            if (x[v] != x[u]) {
                int xx = v, uu = u;
                if (x[xx] > x[uu]) {
                    if (taken[{x[uu] + 1, y[uu] - 1}] == 0) {
                        mpp[{uu, xx}] = {x[uu] + 1, y[uu] - 1};
                        taken[{x[uu] + 1, y[uu] - 1}] = 1;
                    }
                    else if (taken[{x[uu] + 1, y[uu] + 1}] == 0) {
                        mpp[{uu, xx}] = {x[uu] + 1, y[uu] + 1};
                        taken[{x[uu] + 1, y[uu] + 1}] = 1;
                    }
                    else assert(0);
                }
                else {
                    if (taken[{x[xx] + 1, y[xx] + 1}] == 0) {
                        mpp[{xx, uu}] = {x[xx] + 1, y[xx] + 1};
                        taken[{x[xx] + 1, y[xx] + 1}] = 1;
                    }
                    else if (taken[{x[xx] + 1, y[xx] - 1}] == 0) {
                        mpp[{xx, uu}] = {x[xx] + 1, y[xx] - 1};
                        taken[{x[xx] + 1, y[xx] - 1}] = 1;
                    }
                    else assert(0);
                }
            }
            else {
                int xx = v, uu = u;
                if (y[xx] > y[uu]) {
                    if (taken[{x[uu] + 1, y[uu] + 1}] == 0) {
                        mpp[{uu, xx}] = {x[uu] + 1, y[uu] + 1};
                        taken[{x[uu] + 1, y[uu] + 1}] = 1;
                    }
                    else if (taken[{x[uu] - 1, y[uu] + 1}] == 0) {
                        mpp[{uu, xx}] = {x[uu] - 1, y[uu] + 1};
                        taken[{x[uu] - 1, y[uu] + 1}] = 1;
                    }
                    else assert(0);
                }
                else {
                    if (taken[{x[xx] - 1, y[xx] + 1}] == 0) {
                        mpp[{xx, uu}] = {x[xx] - 1, y[xx] + 1};
                        taken[{x[xx] - 1, y[xx] + 1}] = 1;
                    }
                    else if (taken[{x[xx] + 1, y[xx] + 1}] == 0) {
                        mpp[{xx, uu}] = {x[xx] + 1, y[xx] + 1};
                        taken[{x[xx] + 1, y[xx] + 1}] = 1;
                    }
                    else assert(0);
                }
            }
            go(u);
        }
    };
    go(st);
    for (int i = 0; i < u.size(); i ++) {
        a.push_back(mpp[{u[i], v[i]}].first);
        b.push_back(mpp[{u[i], v[i]}].second);
        u[i] --;
        v[i] --;
    }
    if (num == n) {
        build(u, v, a, b);
        return 1;
    }
    return 0;
}

Compilation message (stderr)

parks.cpp: In function 'int construct_roads(std::vector<int>, std::vector<int>)':
parks.cpp:132:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  132 |     for (int i = 0; i < u.size(); i ++) {
      |                     ~~^~~~~~~~~~

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