Submission #873188

#	Time	Username	Problem	Language	Result	Execution time	Memory
873188		Ghulam_Junaid	Pipes (CEOI15_pipes)	C++17	100 / 100	849 ms	14420 KiB

pipes

#include <bits/stdc++.h>
using namespace std;

const int N = 1e5 + 1;
int h[N], mnh[N], edges;
bool vis[N];
vector<pair<int, int>> g[N];

int root1(int& v){
    return (h[v] == -1 ? v : h[v] = root1(h[v]));
}

int root2(int& v){
    return (mnh[v] == -1 ? v : mnh[v] = root2(mnh[v]));
}

void merge1(int& u, int& v){    
    int r1 = root1(v);
    int r2 = root1(u);

    h[r1] = r2;

    edges++;
    g[v].push_back({u, edges});
    g[u].push_back({v, edges});
}

void merge2(int& u, int& v){
    int r1 = root2(u);
    int r2 = root2(v);

    if (r1 == r2)
        return;

    mnh[r1] = r2;

    edges++;
    g[v].push_back({u, edges});
    g[u].push_back({v, edges});
}

void dfs(int& v, pair<int, int> prev = {-1, -1}){
    vis[v] = 1;
    if (prev.first == -1)
        h[v] = 0;
    mnh[v] = h[v];

    for (auto& [u, id] : g[v]){
         if (prev.first == u and prev.second == id)
            continue;

        mnh[v] = min(mnh[v], h[u]);

        if (vis[u])
            continue;

        h[u] = h[v] + 1;
        dfs(u, {v, id});
        mnh[v] = min(mnh[v], mnh[u]);

        if (mnh[u] >= h[u])
            printf("%d %d\n", u, v);
            
    }
}

int main(){

    int n, m;
    scanf("%d%d", &n, &m);

    for (int i=1; i<=n; i++)
        h[i] = mnh[i] = -1;

    for (int i=0; i<m; i++){
        int u, v;
        scanf("%d%d", &u, &v);

        if (root1(u) != root1(v))
            merge1(u, v);
        else if (root2(u) != root2(v))
            merge2(u, v);
    }

    for (int i=1; i<=n; i++)
        h[i] = mnh[i] = n + 100;

    for (int v = 1; v <= n; v++)
        if (!vis[v])
            dfs(v);
}

Compilation message (stderr)

pipes.cpp: In function 'int main()':
pipes.cpp:70:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   70 |     scanf("%d%d", &n, &m);
      |     ~~~~~^~~~~~~~~~~~~~~~
pipes.cpp:77:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   77 |         scanf("%d%d", &u, &v);
      |         ~~~~~^~~~~~~~~~~~~~~~

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