Submission #703861

#	Time	Username	Problem	Language	Result	Execution time	Memory
703861		bebra	Connecting Supertrees (IOI20_supertrees)	C++17	21 / 100	192 ms	22284 KiB

supertrees

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

#define dbg(x) cerr << #x << ": " << x << endl;


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

    DSU(int n) {
        parent.resize(n);
        iota(parent.begin(), parent.end(), 0);
        size.assign(n, 1);
        comps_n = n;
    }

    int find(int v) {
        if (parent[v] == v) {
            return v;
        } else {
            return parent[v] = find(parent[v]);
        }
    }

    void unite(int u, int v) {
        if (u == v) return;
        u = find(u);
        v = find(v);
        if (size[u] > size[v]) swap(u, v);
        parent[u] = v;
        size[v] += size[u];
    }
};


int construct(vector<vector<int>> p) {
	int n = p.size();

	vector<vector<int>> g(n, vector<int>(n));

    bool ok = true;
    DSU dsu(n);
    for (int u = 0; u < n; ++u) {
        for (int v = u + 1; v < n; ++v) {
            if (p[u][v] > 0) {
                dsu.unite(u, v);
            }
        }
    }

    map<int, vector<int>> comps;
    for (int v = 0; v < n; ++v) {
        comps[dsu.find(v)].push_back(v);
    }
    
    for (const auto& [c, comp] : comps) {
        int m = comp.size();
        if (m == 1) continue;

        DSU curr_comps(m);

        vector<int> cycle;
        bool has_cycle = false;
        for (int i = 0; i < m; ++i) {
            int u = comp[i];

            bool has_one = false;
            for (int j = 0; j < m; ++j) {
                if (i == j) continue;
                int v = comp[j];

                if (u == v) continue;

                if (p[u][v] == 0) {
                    ok = false;
                    break;
                }
                if (p[u][v] >= 2) {
                    has_cycle = true;
                }
                
                if (p[u][v] == 1) {
                    curr_comps.unite(i, j);
                    has_one = true;
                }
            }
            if (!has_one) {
                cycle.push_back(u);
            }
        }

        if (!has_cycle) {
            for (int i = 0; i < m - 1; ++i) {
                g[comp[i]][comp[i + 1]] = g[comp[i + 1]][comp[i]] = 1;
            }
            continue;
        }
        

        map<int, vector<int>> groupsf;
        for (auto v : comp) {
            if (curr_comps.size[curr_comps.find(v)] > 1) {
                groupsf[curr_comps.find(v)].push_back(v);
            }
        }

        int groups_n = groupsf.size();

        if (groups_n > 2) {
            ok = false;
            break;
        }

        if (groups_n == 2 && cycle.size() < 1) {
            ok = false;
            break;
        }
        if (groups_n == 1 && cycle.size() < 2) {
            ok = false;
            break;
        }
        if (groups_n == 0 && cycle.size() < 3) {
            ok = false;
            break;
        }

        vector<vector<int>> groups(2);
        {
            int i = 0;
            for (const auto& [f, v] : groupsf) {
                groups[i] = v;
                ++i;
            }
        }

        for (int t = 0; t <= 1; ++t) {
            for (auto u : groups[t]) {
                for (auto v : groups[t]) {
                    if (p[u][v] != 1) {
                        ok = false;
                    }
                }
            }
        }
        for (auto u : groups[0]) {
            for (auto v : groups[1]) {
                if (p[u][v] != 2) {
                    ok = false;
                }
            }
        }

        vector<int> line;
        for (auto v : groups[0]) {
            line.push_back(v);
        }
        for (auto v : cycle) {
            line.push_back(v);
        }
        for (auto v : groups[1]) {
            line.push_back(v);
        }

        if ((int)line.size() != m) {
            ok = false;
            break;
        }
        
        for (int i = 0; i < m - 1; ++i) {
            g[line[i]][line[i + 1]] = g[line[i + 1]][line[i]] = 1;
        }

        while (groups_n == 2 && groups[1].empty()) {}

        {
            int u, v;
            if (groups_n == 2) {
                u = groups[0].back();
                v = groups[1][0];
            } else if (groups_n == 1) {
                u = groups[0].back();
                v = cycle.back();
            } else if (groups_n == 0) {
                u = cycle[0];
                v = cycle.back();
            }
            g[u][v] = g[v][u] = 1;
        }
    }


    // for (int i = 0; i < n; ++i) {
    //     for (int j = 0; j < n; ++j) {
    //         if (g[i][j] == 1) {
    //             cout << i << ' ' << j << '\n';
    //         }
    //     }
    //     cout << '\n';
    // }
	if (ok) {
        build(g);
        return 1;
    }
    return 0;
}

// int main() {
//     int n;
//     cin >> n;
//     vector<vector<int>> p(n, vector<int>(n));
//     for (int i = 0; i < n; ++i) {
//         for (int j = 0; j < n; ++j) {
//             cin >> p[i][j];
//         }
//     }
//     construct(p);

// }

Compilation message (stderr)

supertrees.cpp: In function 'int construct(std::vector<std::vector<int> >)':
supertrees.cpp:190:26: warning: 'v' may be used uninitialized in this function [-Wmaybe-uninitialized]
  190 |             g[u][v] = g[v][u] = 1;
      |                          ^
supertrees.cpp:190:29: warning: 'u' may be used uninitialized in this function [-Wmaybe-uninitialized]
  190 |             g[u][v] = g[v][u] = 1;
      |                             ^

• Subtask 1: 11 / 11
• Subtask 2: 10 / 10
• Subtask 3: 0 / 19
• Subtask 4: 0 / 35
• Subtask 5: 0 / 21
• Subtask 6: 0 / 4