Submission #479900

#	Time	Username	Problem	Language	Result	Execution time	Memory
479900		couplefire	Connecting Supertrees (IOI20_supertrees)	C++17	96 / 100	214 ms	26168 KiB

supertrees

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

struct DSU{
    int n; vector<int> fa, siz;
    vector<vector<int>> comps;
    void init(int _n){
        n = _n;
        fa.resize(n); siz.assign(n, 1);
        iota(fa.begin(), fa.end(), 0);
        comps.resize(n);
        for(int i = 0; i<n; ++i)
            comps[i].push_back(i);
    }
    int find(int v){return v==fa[v]?v:fa[v]=find(fa[v]);}
    void unite(int u, int v){
        u = find(u), v =find(v);
        if(u==v) return;
        if(siz[u]>siz[v]) swap(u, v);
        for(auto x : comps[u])
            comps[v].push_back(x);
        comps[u].clear(); fa[u] = v;
    }
};

int construct(vector<vector<int>> paths){
    int n = paths.size();
    DSU d1; d1.init(n);
    for(int i = 0; i<n; ++i)
        for(int j = i+1; j<n; ++j)
            if(paths[i][j]) d1.unite(i, j);
    vector<vector<int>> res(n, vector<int>(n, 0));
    for(auto c : d1.comps){
        if(c.empty()) continue;
        int m = c.size();
        for(int i = 0; i<m; ++i)
            for(int j = i+1; j<m; ++j)
                if(!paths[c[i]][c[j]]) return 0;
        DSU d2; d2.init(m);
        for(int i = 0; i<m; ++i)
            for(int j = i+1; j<m; ++j)
                if(paths[c[i]][c[j]]==1) d2.unite(i, j);
        for(auto x : d2.comps)
            for(int i = 0; i<x.size(); ++i)
                for(int j = i+1; j<x.size(); ++j)
                    if(paths[c[x[i]]][c[x[j]]]!=1) return 0;
        vector<int> good;
        for(auto x : d2.comps){
            if(!x.size()) continue;
            good.push_back(c[x[0]]);
            for(int i = 0; i<(int)x.size()-1; ++i)
                res[c[x[i]]][c[x[i+1]]] = res[c[x[i+1]]][c[x[i]]] = 1;
        }
        if((int)good.size()==1) continue;
        if((int)good.size()==2) return 0;
        good.push_back(good[0]);
        for(int i = 0; i<(int)good.size()-1; ++i)
            res[good[i]][good[i+1]] = res[good[i+1]][good[i]] = 1;
    }
    build(res); return 1;
}

Compilation message (stderr)

supertrees.cpp: In function 'int construct(std::vector<std::vector<int> >)':
supertrees.cpp:45:29: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   45 |             for(int i = 0; i<x.size(); ++i)
      |                            ~^~~~~~~~~
supertrees.cpp:46:35: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   46 |                 for(int j = i+1; j<x.size(); ++j)
      |                                  ~^~~~~~~~~

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