Submission #212780

#	Time	Username	Problem	Language	Result	Execution time	Memory
212780		Alexa2001	Chameleon's Love (JOI20_chameleon)	C++17	100 / 100	54 ms	512 KiB

chameleon

#include "chameleon.h"
#include <vector>
#include <bits/stdc++.h>

using namespace std;

namespace
{
    vector<int> bad[2000];
    int n;
    int color[2000];
}

void dfs(int node, int C = 1)
{
    color[node] = C;
    for(auto it : bad[node])
        if(!color[it])
            dfs(it, 3 - C);
}

static void color_nodes()
{
    memset(color, 0, sizeof(color));

    int i;
    for(i=1; i<=2*n; ++i)
        if(!color[i])
            dfs(i);
}

void add_edge(int x, int y)
{
    bad[x].push_back(y);
    bad[y].push_back(x);
}

void cbin(int node, const vector<int> &v)
{
    int i, st, dr, mid;
    st = 0; dr = v.size() - 1;

    while(1)
    {
        vector<int> q;
        for(i=st; i<=dr; ++i) q.push_back(v[i]);
        q.push_back(node);

        if(Query(q) == q.size()) return;

        while(st < dr)
        {
            mid = (st + dr) / 2;
            q.clear();
            for(i=st; i<=mid; ++i) q.push_back(v[i]);
            q.push_back(node);

            if(Query(q) == q.size()) st = mid + 1;
                else dr = mid;
        }

        add_edge(node, v[st]);

        ++st; dr = v.size() - 1;
    }
}

static void find_bad()
{
    int i, j;

    for(i=1; i<=2*n; ++i)
    {
        color_nodes();

        vector<int> A[2];

        for(j=1; j<i; ++j)
            A[color[j] - 1].push_back(j);

        cbin(i, A[0]);
        cbin(i, A[1]);
    }
}

static void find_opposite()
{
    color_nodes();

    int i, j, k;

    for(i=1; i<=2*n; ++i)
    {
        if(color[i] == 2) continue;

        for(auto it : bad[i])
            assert(color[i] + color[it] == 3);

        if(bad[i].size() == 1)
            Answer(i, bad[i][0]);
        else
        {
            assert(bad[i].size() == 3);

            bool ok[3];
            ok[0] = ok[1] = ok[2] = 1;

            for(j=0; j<3; ++j)
                for(k=j+1; k<3; ++k)
                {
                    vector<int> vv = {i, bad[i][j], bad[i][k]};
                    if(Query(vv) == 1) ok[3 - j - k] = 0;
                }

            for(j=0; j<3; ++j)
            {
                int all[2], nr = 0;

                for(auto it : bad[bad[i][j]])
                    if(it != i)
                        all[nr++] = it;

                vector<int> vv = {bad[i][j], all[0], all[1]};
                if(vv.back() == i) continue;

                if(Query(vv) == 1) ok[j] = 0;
            }

            bool cnt = 0;
            for(j=0; j<3; ++j) cnt += ok[j];
            assert(cnt == 1);

            for(j=0; j<3; ++j)
                if(ok[j])
                    Answer(i, bad[i][j]);
        }
    }
}

void Solve(int N)
{
    n = N;
    find_bad();
    find_opposite();
}

Compilation message (stderr)

chameleon.cpp: In function 'void cbin(int, const std::vector<int>&)':
chameleon.cpp:49:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         if(Query(q) == q.size()) return;
            ~~~~~~~~~^~~~~~~~~~~
chameleon.cpp:58:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             if(Query(q) == q.size()) st = mid + 1;
                ~~~~~~~~~^~~~~~~~~~~

• Subtask 1: 4 / 4
• Subtask 2: 20 / 20
• Subtask 3: 20 / 20
• Subtask 4: 20 / 20
• Subtask 5: 36 / 36