Submission #1073031

#	Time	Username	Problem	Language	Result	Execution time	Memory
1073031		mc061	Connecting Supertrees (IOI20_supertrees)	C++17	100 / 100	163 ms	28272 KiB

supertrees

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

const int N = 1001;

struct DSU {
    vector<int> p;
    vector<vector<int>> els;
    DSU() {
        p.resize(N);
        els.resize(N);
        iota(p.begin(), p.end(), 0);
        for (int i = 0; i < N; ++i) {
            els[i].push_back(i);
        }
    }
    int get(int a) {
        return p[a] = (a == p[a] ? a : get(p[a]));
    }
    void merge(int a, int b) {
        int x = get(a);
        int y = get(b);
        if (x == y) return;
        if (els[x].size() > els[y].size()) {
            swap(x, y);
        }
        p[x] = y;
        while (els[x].size()) els[y].push_back(els[x].back()), els[x].pop_back();
    }
};

vector<int> graph[N];
vector<vector<int>> cur_p(N, vector<int>(N, 0));

int cnt[N]={};
vector<int> path;
void dfs(int start, int v) {
    path.push_back(v);
    cur_p[start][v]++;
    cnt[v]++;
    for (int u : graph[v]) {
        if (cnt[u] == 0) dfs(start, u);
    }
    cnt[v]--;
    path.pop_back();
}

void build(vector<vector<int>> b);
int construct(vector<vector<int>> p) {
    DSU lines;
    const int n = p.size();
    vector<vector<int>> b(n, vector<int>(n, 0));
    for (int i = 0; i < n; ++i) {
        for (int j = i+1; j < n; ++j) {
            if (p[i][j] == 1) {
                int x = lines.get(i);
                int y = lines.get(j);
                if (x != y) {
                    b[i][j] = b[j][i] = 1;
                    lines.merge(x, y);
                }
            }
        }
    }
    DSU comps;
    for (int i = 0; i < n; ++i) {
        for (int j = i+1; j < n; ++j) {
            if (p[i][j] > 0) comps.merge(i, j);
        }
    }
    vector<bool> vis(n, false);
    for (int i = 0; i < n; ++i) {
        int j = comps.get(i);
        if (vis[j]) continue;
        vis[j] = true;
        vector<int> vs = comps.els[j];
        vector<int> twos;
        vector<bool> vis_lines(n, false);
        for (int k = 0; k < vs.size(); ++k) {
            int v = vs[k];
            if (vis_lines[lines.get(v)]) continue;
            int u = lines.els[lines.get(v)].front();
            twos.push_back(u);
            vis_lines[lines.get(v)] = true;
        }
        if (twos.size() == 1) continue;
        for (int k = 0; k < twos.size(); ++k) {
            int nxt = (k+1)%twos.size();
            b[twos[k]][twos[nxt]] = b[twos[nxt]][twos[k]] = 1;
        }
    }
    for (int i = 0; i < n; ++i) {
        for (int j = i+1; j < n; ++j) {
            if (b[i][j]) graph[i].push_back(j), graph[j].push_back(i);
        }
    }
    for (int i = 0; i < n; ++i) {
        dfs(i, i);
    }
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < n; ++j) {
            if (cur_p[i][j] != p[i][j]) return 0;
        }
    }
    build(b);
    return true;
}

Compilation message (stderr)

supertrees.cpp: In function 'int construct(std::vector<std::vector<int> >)':
supertrees.cpp:79:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   79 |         for (int k = 0; k < vs.size(); ++k) {
      |                         ~~^~~~~~~~~~~
supertrees.cpp:87:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   87 |         for (int k = 0; k < twos.size(); ++k) {
      |                         ~~^~~~~~~~~~~~~

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