Submission #1057143

#	Time	Username	Problem	Language	Result	Execution time	Memory
1057143		arbuzick	Connecting Supertrees (IOI20_supertrees)	C++17	100 / 100	153 ms	24188 KiB

supertrees

#include "supertrees.h"

#include <bits/stdc++.h>

using namespace std;

struct DSU {
    int n;
    vector<int> sz, p;

    DSU(int _n) {
        n = _n;
        sz.assign(n, 1);
        p.resize(n);
        iota(p.begin(), p.end(), 0);
    }

    int pr(int v) {
        if (p[v] == v) {
            return v;
        }
        return p[v] = pr(p[v]);
    }

    void unite(int a, int b) {
        a = pr(a), b = pr(b);
        if (a == b) {
            return;
        }
        if (sz[a] < sz[b]) {
            swap(a, b);
        }
        p[b] = a;
        sz[a] += sz[b];
    }
};

int construct(vector<vector<int>> p) {
    int n = p.size();
    vector<vector<int>> answer(n, vector<int>(n));
    for (int i = 0; i < n; ++i) {
        for (int j = i + 1; j < n; ++j) {
            if (p[i][j] == 3) {
                return 0;
            }
        }
    }

    DSU d0(n);
    for (int i = 0; i < n; ++i) {
        for (int j = i + 1; j < n; ++j) {
            if (p[i][j] != 0) {
                d0.unite(i, j);
            }
        }
    }
    for (int i = 0; i < n; ++i) {
        for (int j = i + 1; j < n; ++j) {
            if (d0.pr(i) == d0.pr(j) && p[i][j] == 0) {
                return 0;
            }
        }
    }

    DSU d1(n);
    for (int i = 0; i < n; ++i) {
        for (int j = i + 1; j < n; ++j) {
            if (p[i][j] == 1) {
                d1.unite(i, j);
            }
        }
    }
    for (int i = 0; i < n; ++i) {
        for (int j = i + 1; j < n; ++j) {
            if (d1.pr(i) == d1.pr(j) && p[i][j] != 1) {
                return 0;
            }
        }
        if (d1.pr(i) != i) {
            answer[d1.pr(i)][i] = answer[i][d1.pr(i)] = 1;
        }
    }

    DSU d2(n);
    for (int i = 0; i < n; ++i) {
        for (int j = i + 1; j < n; ++j) {
            if (p[i][j] == 2) {
                d2.unite(i, j);
            }
        }
    }
    vector<vector<int>> cycles(n);
    for (int i = 0; i < n; ++i) {
        if (d2.sz[d2.pr(i)] != 1 && i == d1.pr(i)) {
            cycles[d2.pr(i)].push_back(i);
        }
    }
    for (int i = 0; i < n; ++i) {
        if (cycles[i].size() == 2) {
            return 0;
        }
        for (int j = 0; j < (int)cycles[i].size(); ++j) {
            int nxt = j + 1;
            if (nxt == (int)cycles[i].size()) {
                nxt = 0;
            }
            answer[cycles[i][j]][cycles[i][nxt]] = answer[cycles[i][nxt]][cycles[i][j]] = 1;
        }
    }

    build(answer);
    return 1;
}

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