Submission #291507

#	Time	Username	Problem	Language	Result	Execution time	Memory
291507		davooddkareshki	Pipes (CEOI15_pipes)	C++17	60 / 100	1152 ms	59628 KiB

pipes

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

//#define int long long
#define F first
#define S second
#define pii pair<int,int>
#define mpr make_pair

typedef long long ll;

const int maxn = 1e5+10;
const int mod = 1e9+7;
const int inf = 1e9+10;

int n, m, q;

struct dsu
{
    int par[maxn];
    dsu() {memset(par, -1, sizeof par);}
    int get_par(int v)
    {
        if(par[v] < 0) return v;
        return par[v] = get_par(par[v]);
    }

    void merg(int u, int v)
    {
        u = get_par(u);
        v = get_par(v);

        if(u == v) return;

        if(par[u] < par[v]) swap(u,v);
        par[v] += par[u];
        par[u] = v;
    }

    bool ask(int u, int v) {return (get_par(u) == get_par(v));}
} G, T;

/// G --> kole graph
/// T --> molefe haye 2hamband yali graph

vector<pii> g[maxn];
bool mark[maxn]; int la[maxn];

void pfs(int v, int p = 0)
{
    mark[v] = 1;
    for(auto e : g[v])
    {
        int u = e.F;
        if(mark[u]) {la[v]++; la[u]--;}
    }
    for(auto e : g[v])
    {
        int u = e.F;
        if(!mark[u]) pfs(u,v);
    }
    la[p]++; la[v]--;
}

vector<int> ans;
void dfs(int v, int id = -1)
{
    mark[v] = 1;
    for(auto e : g[v])
    {
        int u = e.F, ID = e.S;
        if(!mark[u])
        {
            dfs(u,ID);
            la[v] += la[u];
        }
    }

    if(la[v] == 0 && id >= 0)
        ans.push_back(id);
}

signed main()
{
    ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);

    cin>> n >> m;
    vector<pii> edge;
    for(int i = 1, u, v; i <= m; i++)
    {
        cin>> u >> v;

        if(!G.ask(u,v))
        {
            G.merg(u,v);
            edge.push_back({u,v});
        }
        else
            T.merg(u,v);
    }

    int i = 0;
    for(auto e : edge)
    {
        int u = T.get_par(e.F), v = T.get_par(e.S);
        g[u].push_back({v,i});
        g[v].push_back({u,i});
        i++;
    }

    for(int i = 1; i <= n; i++)
        if(!mark[i]) pfs(i);
    memset(mark, 0, sizeof mark);
    for(int i = 1; i <= n; i++)
        if(!mark[i]) dfs(i);

    for(auto x : ans)
        cout<< edge[x].F <<" "<< edge[x].S <<"\n";
}
/*
10 11
1 7
1 8
1 6
2 8
6 7
5 8
2 5
2 3
2 4
3 4
10 9
*/

• 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: 0 / 10
• Subtask 8: 0 / 10
• Subtask 9: 0 / 10
• Subtask 10: 0 / 10