Submission #956561

#	Time	Username	Problem	Language	Result	Execution time	Memory
956561		KK_1729	Connecting Supertrees (IOI20_supertrees)	C++17	0 / 100	0 ms	348 KiB

supertrees

#include "supertrees.h"
#include <vector>
#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define FOR(i,a,b) for (int i = (a); i < (b); ++i)
struct UFDS {
    vector<int> link, siz;
    UFDS(int n) : link(n), siz(n, 1) { iota(link.begin(), link.end(), 0); } //each element as its own subset, with size 1
    int findRoot(int x) {
        if(x == link[x]) return x;
        return link[x] = findRoot(link[x]);
        /*
        A shorter way of writing the following is:
        return x == link[x]  ? x : link[x]  =  findRoot(link[x]);  
        */
    }
    bool same(int x, int y) { return findRoot(x) == findRoot(y); }
    bool unite(int x, int y) {
        x = findRoot(x);
        y = findRoot(y);
        if (x == y)
            return false;
        if (siz[x] < siz[y]) swap(x, y);
        siz[x] += siz[y];
        link[y] = x;
        return true;
    }
    int size(int x) { return siz[findRoot(x)]; }
};


int construct(std::vector<std::vector<int>> p) {
	int n = p.size();
	std::vector<std::vector<int>> answer;
	for (int i = 0; i < n; i++) {
		std::vector<int> row;
		row.resize(n);
		answer.push_back(row);
	}


	UFDS ds(n);
	vector<int> cycle(n);
	for (int i = 0; i < n; ++i){
		for (int j = 0; j < n; ++j){
			if (i == j) continue;
			if (p[i][j] == 2){
				ds.unite(i, j);
				cycle[i] = 1;
			}
			if (p[i][j] == 1) cycle[i] = 0;
			if (p[i][j] == 0){
				if (ds.same(i, j)) return 0;
			}
		}
	}


	vector<vector<int>> parents(n);

	for (int i = 0; i < n; ++i) parents[ds.findRoot(i)].push_back(i);
	
	for (auto item: parents){
		int u = item.size();
		vector<int> cyc;
		vector<int> normal;
		for (auto x: item){
			if (cycle[x]) cyc.pb(x);
			else normal.pb(x);
		}

		int v = normal.size();
		FOR(i,0,v-1){
			answer[normal[i]][normal[i+1]] = 1;
			answer[normal[i+1]][normal[i]] = 1;
		}

		if (cyc.size() <= 2) return 0;
		v = cyc.size();

		FOR(i,0,v-1){

			answer[cyc[i]][cyc[i+1]] = 1;
			answer[cyc[i+1]][cyc[i]] = 1;
		}
		answer[cyc[0]][cyc[v-1]] = 1;
		answer[cyc[v-1]][cyc[0]] = 1;

		answer[normal[0]][cyc[0]] = 1;
		answer[cyc[0]][normal[0]] = 1;
	}
	build(answer);
	return 1;
}

Compilation message (stderr)

supertrees.cpp: In function 'int construct(std::vector<std::vector<int> >)':
supertrees.cpp:65:7: warning: unused variable 'u' [-Wunused-variable]
   65 |   int u = item.size();
      |       ^

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