Submission #1193313

#	Time	Username	Problem	Language	Result	Execution time	Memory
1193313		CrabCNH	Pipes (CEOI15_pipes)	C++20	20 / 100	1732 ms	131072 KiB

pipes

#include <bits/stdc++.h>

#define task   "BriantheCrab"

#define pii    pair <int, int>
#define fi     first
#define se     second
#define szf    sizeof
#define sz(s)  (int)((s).size())

using namespace std;

template <class T> void mini (T &t, T f) {if (t > f) t = f;}
template <class T> void maxi (T &t, T f) {if (t < f) t = f;}

const int maxN = 1e5 + 5;
const int maxM = 6e6 + 1;
const int mod = 1e9 + 7;

int n, m;
int timeDfs = 0;
int low[maxN], num[maxN];
vector <pii> adj[maxN];
set <pii> bridges;

void dfs (int u, int parent, int pE) {
    num[u] = low[u] = ++timeDfs;
    for (auto [v, id] : adj[u]) {
        if (id == pE) {
            continue;
        }
        if (num[v]) {
            mini (low[u], num[v]);
        } 
        else {
            dfs (v, u, id);
            mini (low[u], low[v]);
            if (low[v] > num[u]) {
                bridges.insert ({min (u, v), max (u, v)});
            }
        }
    }
}

void solve () {
    cin >> n >> m;
    for (int i = 1; i <= m; i ++) {
        int u, v;
        cin >> u >> v;
        adj[u].push_back ({v, i});
        adj[v].push_back ({u, i});
    }
    for (int i = 1; i <= n; i ++) {
        if (num[i] == 0) {
            dfs (i, i, -1);
        }
    }
    for (auto [x, y] : bridges) {
        cout << x << ' ' << y << '\n';
    }
    return;
}

signed main () {
    cin.tie (nullptr) -> sync_with_stdio (false);
    if (fopen (task".inp", "r")) {
        freopen (task".inp", "r", stdin);
        freopen (task".out", "w", stdout);
    }
    int t = 1;
    //cin >> t;
    while (t --) {
        solve ();
    } 
    return 0;
}
// thfdgb

Compilation message (stderr)

pipes.cpp: In function 'int main()':
pipes.cpp:67:17: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   67 |         freopen (task".inp", "r", stdin);
      |         ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
pipes.cpp:68:17: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   68 |         freopen (task".out", "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