Submission #921873

#	Time	Username	Problem	Language	Result	Execution time	Memory
921873		boris_mihov	Meetings (JOI19_meetings)	C++17	100 / 100	811 ms	1412 KiB

meetings

#include "meetings.h"
#include <algorithm>
#include <iostream>
#include <numeric>
#include <cassert>
#include <random>
#include <vector>
 
typedef long long llong;
const int MAXN = 2000 + 10;
const int INF  = 1e9;
 
int n;
int sz[MAXN];
bool bl[MAXN];
int perm[MAXN];
bool alreadyAdded[MAXN];
std::vector <int> g[MAXN];
std::vector <int> c[MAXN];
std::vector <int> real[MAXN];
std::mt19937 rng(69420);
 
void removeEdge(int u, int v)
{
    if (u == -1 || v == -1)
    {
        return;
    }
    
    for (int &x : g[u])
    {
        if (x == v)
        {
            std::swap(x, g[u].back());
            g[u].pop_back();
            break;
        }
    }
 
    for (int &x : g[v])
    {
        if (x == u)
        {
            std::swap(x, g[v].back());
            g[v].pop_back();
            break;
        }
    }
}
 
void addEdge(int u, int v)
{
    if (u == -1 || v == -1)
    {
        return;
    }
 
    g[u].push_back(v);
    g[v].push_back(u);
}
 
void calcSize(int node, int par)
{
    sz[node] = 1;
    for (const int &u : g[node])
    {
        if (u == par || bl[u])
        {
            continue;
        }
 
        calcSize(u, node);
        sz[node] += sz[u];
    }
}
 
int findCentroid(int node, int par, int compSz)
{
    for (const int &u : g[node])
    {
        if (!bl[u] && u != par && sz[u] > compSz / 2)
        {
            return findCentroid(u, node, compSz);
        }
    }
 
    return node;
}
 
int decompose(int node)
{
    calcSize(node, -1);
    int cntr = findCentroid(node, -1, sz[node]);
    bl[cntr] = true;
 
    for (const int &u : g[cntr])
    {
        if (bl[u])
        {
            continue;
        }
 
        c[cntr].push_back(decompose(u));
        real[cntr].push_back(u);
    }
 
    return cntr;
}
 
void search(int node, int added)
{
    bool addedEdge = false;
    for (int i = 0 ; i < c[node].size() ; i += 2)
    {
        if (i == c[node].size() - 1)
        {
            int res = Query(node, real[node][i], added);
            if (res == node)
            {
                continue;
            }

            if (res != node && res != real[node][i] && res != added)
            {
                removeEdge(node, real[node][i]);
                addEdge(node, res);
                addEdge(res, real[node][i]);
                addEdge(res, added);
                alreadyAdded[res] = true;
                return;
            }
    
            if (res == added)
            {
                removeEdge(node, real[node][i]);
                if (!addedEdge) 
                {
                    addEdge(node, added);
                    addedEdge = true;
                }
    
                addEdge(real[node][i], added);
                continue;
            }
    
            if (res == real[node][i])
            {
                search(c[node][i], added);
                return;
            }

            assert(false);
        }

        int res = Query(real[node][i], real[node][i + 1], added);
        // std::cout << "res is: " << real[node][i] << ' ' << real[node][i + 1] << ' ' << added << " = " << res << '\n';
        if (res == node)
        {
            continue;
        }

        if (res == added)
        {
            int res2 = Query(node, real[node][i], added);
            if (res == res2)
            {
                removeEdge(node, real[node][i]);
                if (!addedEdge) 
                {
                    addEdge(node, added);
                    addedEdge = true;
                }
    
                addEdge(real[node][i], added);
            } else
            {
                removeEdge(node, real[node][i + 1]);
                if (!addedEdge) 
                {
                    addEdge(node, added);
                    addedEdge = true;
                }
    
                addEdge(real[node][i + 1], added);
            }

            return;
        }

        if (res == real[node][i])
        {
            search(c[node][i], added);
            return;
        }

        if (res == real[node][i + 1])
        {
            search(c[node][i + 1], added);
            return;
        }
    
        if (res != node && res != real[node][i] && res != added)
        {
            int res2 = Query(node, real[node][i], added);
            if (res == res2)
            {
                removeEdge(node, real[node][i]);
                addEdge(node, res);
                addEdge(res, real[node][i]);
                addEdge(res, added);
                alreadyAdded[res] = true;
            } else
            {
                removeEdge(node, real[node][i + 1]);
                addEdge(node, res);
                addEdge(res, real[node][i + 1]);
                addEdge(res, added);
                alreadyAdded[res] = true;
            }
            return;
        
        }

        assert(false);
    }
 
    if (!addedEdge)
    {
        addEdge(node, added);
    }
}
 
void Solve(int N) 
{
    n = N;
    std::iota(perm, perm + n, 0);
    std::shuffle(perm, perm + n, rng);

    for (int i = 0 ; i < n ; ++i)
    {
        g[i].clear();
        c[i].clear();
        real[i].clear();
    }
 
    g[perm[0]].push_back(perm[1]);
    g[perm[1]].push_back(perm[0]);
 
    // std::cout << "edge: " << perm[0] << ' ' << perm[1] << '\n';
    for (int i = 2 ; i < n ; ++i)
    {
        // std::cout << "current: " << perm[i] << '\n';
        if (alreadyAdded[perm[i]])
        {
            continue;
        }

        for (int j = 0 ; j < n ; ++j)
        {
            c[j].clear();
            real[j].clear();
            std::shuffle(g[j].begin(), g[j].end(), rng);
        }
 
        std::fill(bl, bl + n, false);
        int root = decompose(perm[0]);        
        search(root, perm[i]);
    }
    
    for (int i = 0 ; i < n ; ++i)
    {
        for (const int &u : g[i])
        {
            if (i < u)
            {
                Bridge(i, u);
            }
        }
    }
}

Compilation message (stderr)

meetings.cpp: In function 'void search(int, int)':
meetings.cpp:113:24: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  113 |     for (int i = 0 ; i < c[node].size() ; i += 2)
      |                      ~~^~~~~~~~~~~~~~~~
meetings.cpp:115:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  115 |         if (i == c[node].size() - 1)
      |             ~~^~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 7 / 7
• Subtask 2: 10 / 10
• Subtask 3: 12 / 12
• Subtask 4: 71 / 71