Submission #550086

#	Time	Username	Problem	Language	Result	Execution time	Memory
550086		SmolBrain	Pipes (CEOI15_pipes)	C++17	20 / 100	891 ms	65536 KiB

pipes

// Om Namah Shivaya
// GM in 107 days

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;

template <class T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

typedef long long int ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL)
#define endl '\n'
#define pb push_back
#define conts continue
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define yes cout << "Yes" << endl
#define no cout << "No" << endl
#define ff first
#define ss second
#define ceil2(x,y) ((x+y-1) / (y))
#define sz(a) a.size()
#define setbits(x) __builtin_popcountll(x)
#ifndef ONLINE_JUDGE
#define debug(x) cout << #x <<" = "; print(x); cout << endl
#else
#define debug(x)
#endif

#define rep(i,n) for(int i = 0; i < n; ++i)
#define rep1(i,n) for(int i = 1; i <= n; ++i)
#define rev(i,s,e) for(int i = s; i >= e; --i)
#define trav(i,a) for(auto &i : a)

bool iseven(ll n) {if ((n & 1) == 0) return true; return false;}

void print(ll t) {cout << t;}
void print(int t) {cout << t;}
void print(string t) {cout << t;}
void print(char t) {cout << t;}
void print(double t) {cout << t;}
void print(ld t) {cout << t;}

template <class T, class V> void print(pair <T, V> p);
template <class T> void print(vector <T> v);
template <class T> void print(set <T> v);
template <class T, class V> void print(map <T, V> v);
template <class T> void print(multiset <T> v);
template <class T, class V> void print(pair <T, V> p) {cout << "{"; print(p.ff); cout << ","; print(p.ss); cout << "}";}
template <class T> void print(vector <T> v) {cout << "[ "; for (T i : v) {print(i); cout << " ";} cout << "]";}
template <class T> void print(set <T> v) {cout << "[ "; for (T i : v) {print(i); cout << " ";} cout << "]";}
template <class T> void print(multiset <T> v) {cout << "[ "; for (T i : v) {print(i); cout << " ";} cout << "]";}
template <class T, class V> void print(map <T, V> v) {cout << "[ "; for (auto i : v) {print(i); cout << " ";} cout << "]";}
template<typename T> void amin(T &a, T b) { a = min(a, b); }
template<typename T> void amax(T &a, T b) { a = max(a, b); }

void usaco(string filename) {
    freopen((filename + ".in").c_str(), "r", stdin);
    freopen((filename + ".out").c_str(), "w", stdout);
}

const int MOD = 1e9 + 7;
const int maxn = 5000;
const int inf1 = 1e9 + 5;
const ll inf2 = ll(1e18) + 5;

int n, m;
vector<array<int, 3>> edges;
vector<int> start(maxn, inf1), tin(maxn), low(maxn, inf1);
bitset<maxn> vis;
int timer = 1;

void dfs(int node, int previd) {
    vis[node] = 1;
    tin[node] = low[node] = timer++;

    int pos = start[node];

    for (int i = pos; i < m and edges[i][0] == node; ++i) {
        int child = edges[i][1], id = edges[i][2];

        if (vis[child]) {
            if (id != previd) {
                // back edge
                amin(low[node], tin[child]);
            }
        }
        else {
            dfs(child, id);
            amin(low[node], low[child]);

            if (node == 0 and child == 4) {
                debug(tin[node]);
                debug(low[child]);
            }

            if (low[child] > tin[node]) {
                // bridge
                cout << node + 1 << " " << child + 1 << endl;
            }
        }
    }
}

void solve(int test_case)
{
    // http://lagodiuk.github.io/computer_science/2016/12/19/efficient_adjacency_lists_in_c.html
    cin >> n >> m;
    rep(i, m) {
        int u, v; cin >> u >> v;
        u--, v--;

        edges.pb({u, v, i});
        edges.pb({v, u, i});
    }

    m *= 2;

    sort(all(edges));
    start[edges[0][0]] = 0;

    rep1(i, m - 1) {
        if (edges[i][0] != edges[i - 1][0]) {
            start[edges[i][0]] = i;
        }
    }

    rep(i, n) {
        if (vis[i]) conts;
        dfs(i, -1);
    }
}

int main()
{
    fastio;

    int t = 1;
    // cin >> t;
    rep1(i, t) {
        solve(i);
    }

    return 0;
}

Compilation message (stderr)

pipes.cpp: In function 'void usaco(std::string)':
pipes.cpp:64:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   64 |     freopen((filename + ".in").c_str(), "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
pipes.cpp:65:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   65 |     freopen((filename + ".out").c_str(), "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 0 / 10
• Subtask 4: 0 / 10
• Subtask 5: 0 / 10
• Subtask 6: 0 / 10
• Subtask 7: 0 / 10
• Subtask 8: 0 / 10
• Subtask 9: 0 / 10
• Subtask 10: 0 / 10