제출 #480822

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
480822		silverfox	Network (BOI15_net)	C++14	0 / 100	6 ms	10444 KiB

net

/*
UWOZH SQ ATGZVJNZS

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GZ XPWZU WGZV KZM TIXVJVPO.

MW QWF OVZWL EJ GFHG ECMJ, QWF HEP TM TNWLWL YJXZXQNVXZGV FIHVJ BSZ
TIGDTNMFFA ZA WVUBTJR 512© FX BSZ HZYQEVP DATWZREACX XSGQZTBLK SKE (YQTS)
BZ ZJWWKE MIDGDLG SW LPP VFFNM-CZTFJBPY MEXZTIKVEMYOW.
*/

#include <algorithm>
#include <utility>
#include <fstream>
#include <iomanip>
#include <iostream>
#include <sstream>
#include <climits>
#include <cctype>
#include <string>
#include <map>
#include <set>
#include <unordered_map>
#include <unordered_set>
#include <vector>
#include <random>
#include <cmath>
#include <queue>
#include <stack>
#include <cstring>
#include <limits>
using namespace std;

#pragma GCC optimize("O3")
#define TASK "BLUEHOUSE"
#define lnBr cout << '\n'

const int maxn = 2e5;
bool isBridge[maxn+1];
int num[maxn+1], low[maxn+1];

int d[maxn+1];

int Parent(int u)
{
    if (d[u] < 0) {return u;} return d[u] = Parent(d[u]);
}

void Merge(int x, int y)
{
    if (d[x] > d[y]) { swap(x,y); }
    d[x] += d[y];
    d[y] = x;
}

vector<pair<int, int> > ne[maxn+1];
vector<int> comp[maxn+1];

int timer = 0;
void dfs(int u, int par)
{
    timer++; low[u] = num[u] = timer;
    for (auto e : ne[u])
    {
        int v = e.first, idx = e.second;
        if (v == par) {continue;}

        if (num[v] == 0)
        {
            dfs(v, u);
            low[u] = min(low[u], low[v]);
            if (low[v] == num[v]) //isbridge
            {
                isBridge[idx] = true;
            }
        }
        else
        {
            low[u] = min(low[u], num[v]);
        }
    }

    //check for previous bridge
    if (par != -1)
    {
        int p1 = Parent(u), p2 = Parent(par);
        if (num[u] > low[u]) //isBridge - not
        {
            if (p1 != p2) {Merge(p1, p2); }
        }
        else
        {
            if (p1 != p2)
            {
                comp[p1].push_back(p2);
                comp[p2].push_back(p1);
            }
        }
    }
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr); cout.tie(nullptr);

    if (fopen(TASK".INP", "r"))
    {
        freopen(TASK".INP", "r", stdin);
        freopen(TASK".OUT", "w", stdout);
    }

    int n,m; cin >> n >> m; memset(d, -1, sizeof(d));
    for (int i = 1; i <= m; i++)
    {
        int u,v; cin >> u >> v;
        isBridge[i] = false;
        ne[u].push_back({v, i});
        ne[v].push_back({u, i});
    }

    for (int i = 1; i <= n; i++)
    {
        if (num[i] == 0)
        {
            dfs(i, -1);
        }
    }

    //check compression -> check complete, dfs is right
    /*for (int i = 1; i <= n; i++)
    {
        cout << i << " : ";
        for (int v : comp[i])
        {
            cout << v << " ";
        }
        cout << '\n';
    }*/

    int cnt = 0; int root; vector<int> leaves; int k;
    for (int i = 1; i <= n; i++)
    {
        if (comp[i].size() > 0)
        {
            root = i;
            if (comp[i].size() == 1) {cnt++; leaves.push_back(i); }
            if (comp[i].size() >= 2) {k = i;}
        }
    }
    //int res = (cnt/2) + ((cnt % 2 == 0) ? 0 : 1);
    //cout << res << '\n';
    /*set<int> ll;
    for (int x : leaves) {ll.insert(x);} leaves.clear();

    for (int x : ll)
    {
        bool able = false;
        for (int v : comp[x])
        {
            if (ll.find(v) != ll.end())
            {
                able = true; //break
            }
        }
        if (!able) {leaves.push_back(x); }
    }
    cnt = leaves.size();*/
    int res = (cnt/2) + ((cnt % 2 == 0) ? 0 : 1);
    cout << res << '\n';

    if (cnt%2==0)
    {
        for (int i = 0; i < leaves.size(); i+=2)
        {
            cout << leaves[i] << " " << leaves[i+1] << '\n';
        }
    }
    else
    {
        while(true) {cout << "test";}
        /*for (int i = 0; i < leaves.size(); i+=2)
        {
            cout << leaves[i] << " " << leaves[i+1] << '\n';
        }
        cout << leaves[leaves.size() -1] << " " << k << '\n';*/
    }
}

컴파일 시 표준 에러 (stderr) 메시지

net.cpp: In function 'int main()':
net.cpp:175:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  175 |         for (int i = 0; i < leaves.size(); i+=2)
      |                         ~~^~~~~~~~~~~~~~~
net.cpp:142:22: warning: variable 'root' set but not used [-Wunused-but-set-variable]
  142 |     int cnt = 0; int root; vector<int> leaves; int k;
      |                      ^~~~
net.cpp:142:52: warning: variable 'k' set but not used [-Wunused-but-set-variable]
  142 |     int cnt = 0; int root; vector<int> leaves; int k;
      |                                                    ^
net.cpp:110:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  110 |         freopen(TASK".INP", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
net.cpp:111:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  111 |         freopen(TASK".OUT", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 18
• Subtask 2: 0 / 45
• Subtask 3: 0 / 37