Submission #367010

#	Time	Username	Problem	Language	Result	Execution time	Memory
367010		PurpleCrayon	Connecting Supertrees (IOI20_supertrees)	C++17	100 / 100	259 ms	23788 KiB

supertrees

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

#define ar array
#define sz(v) int(v.size())

int n;

struct DSU {
    vector<int> p, sz;
    void init(int n){ sz.assign(n, 1); p.resize(n); iota(p.begin(), p.end(), 0); }
    int find_set(int v){ return v==p[v]?v:p[v]=find_set(p[v]); }
    bool union_sets(int a, int b){
        if ((a=find_set(a))==(b=find_set(b))) return 0;
        if (sz[a] < sz[b]) swap(a, b);
        p[b]=a, sz[a]+=sz[b], sz[b]=0;
        return 1;
    }
} d;

int construct(vector<vector<int>> g) {
	n = sz(g);
    vector<vector<int>> ans(n, vector<int>(n));


    bool done=0, bad=0;

    [&](){ //handle case with a 3
        if (done || bad) return;

        for (int i = 0; i < n; i++) for (int j = 0; j < n; j++) if (g[i][j] == 3) {
            bad=1; return;
        }
    }();

    
    [&](){ //only 1's (tree)
        if (done || bad) return;

        for (int i = 0; i < n; i++) for (int j = i+1; j < n; j++) if (g[i][j] != 1) return;
        for (int i = 1; i < n; i++) ans[i][0] = ans[0][i] = 1;

        build(ans), done=1;
    }();

    [&](){ //0, 1's (just deal with separate comps)
        if (done || bad) return;

        for (int i = 0; i < n; i++) for (int j = i+1; j < n; j++) if (g[i][j] != 0 && g[i][j] != 1) return;

        d.init(n);
        for (int i = 0; i < n; i++) for (int j = i+1; j < n; j++) if (g[i][j])
            if (d.union_sets(i, j)) ans[i][j] = ans[j][i] = 1;

        for (int i = 0; i < n; i++) for (int j = i+1; j < n; j++)
            if ((d.find_set(i) == d.find_set(j))^bool(g[i][j])) return;

        build(ans), done=1;
    }();

    [&](){ //0, 2's (just deal with separate comps, put everything into cycles instead of trees)
        if (done || bad) return;

        for (int i = 0; i < n; i++) for (int j = i+1; j < n; j++) if (g[i][j] != 0 && g[i][j] != 2) return;

        d.init(n);
        for (int i = 0; i < n; i++) for (int j = i+1; j < n; j++) if (g[i][j])
            d.union_sets(i, j);

        for (int i = 0; i < n; i++) for (int j = i+1; j < n; j++)
            if ((d.find_set(i) == d.find_set(j))^bool(g[i][j])) return;

        vector<vector<int>> comp(n);
        for (int i = 0; i < n; i++) comp[d.find_set(i)].push_back(i);

        for (int i = 0; i < n; i++) if (sz(comp[i]) > 1){
            if (sz(comp[i]) == 2) return;
            for (int j = 0; j < sz(comp[i]); j++){
                int nxt=(j+1)%sz(comp[i]);
                ans[comp[i][j]][comp[i][nxt]] = ans[comp[i][nxt]][comp[i][j]] = 1;
            }
        }

        build(ans), done=1;
    }();

    [&](){ //full sol
        if (done || bad) return;

        d.init(n);
        for (int i = 0; i < n; i++) for (int j = i+1; j < n; j++) if (g[i][j])
            d.union_sets(i, j);

        for (int i = 0; i < n; i++) for (int j = i+1; j < n; j++)
            if ((d.find_set(i) == d.find_set(j))^bool(g[i][j])) return;

        vector<vector<int>> comp(n);
        for (int i = 0; i < n; i++) comp[d.find_set(i)].push_back(i);

        d.init(n);
        auto solve_comp = [&](vector<int> v) -> bool { //they're all in a component
            for (int i : v) for (int j : v) if (i > j && g[i][j]){
                if (g[i][j] == 1){
                    if (d.union_sets(i, j)) ans[i][j] = ans[j][i] = 1;
                } else if (g[i][j] == 2) {
                } else assert(false);
            }
            for (int i : v) for (int j : v) if (i > j && g[i][j] == 2 && d.find_set(i) == d.find_set(j))
                return 0;

            set<int> s;
            for (int i : v) s.insert(d.find_set(i));

            if (sz(s) == 1) return 1;
            else if (sz(s) == 2) return 0;

            vector<int> root(s.begin(), s.end());

            for (int i = 0; i < sz(root); i++){
                int nxt=(i+1)%(sz(root));
                ans[root[i]][root[nxt]] = ans[root[nxt]][root[i]] = 1;
            }
            return 1;
        };

        for (int i = 0; i < n; i++) if (sz(comp[i]) > 1)
            if (!solve_comp(comp[i])) return;

        build(ans), done=1;
    }();

	return !bad && done;
}

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