Submission #391423

#	Time	Username	Problem	Language	Result	Execution time	Memory
391423		ali_tavakoli	Pipes (CEOI15_pipes)	C++14	0 / 100	5097 ms	14948 KiB

pipes

//In The Name Of Allah
#include<bits/stdc++.h>
using namespace std;

typedef long long ll;
#define pb push_back
#define F first
#define S second
//#pragma GCC optimize("Ofast")

const int maxn = 1e5 + 5, maxlog = 19;

int n, m, pr[maxn], x, y, par[maxn][maxlog], h[maxn], cnt[maxn], cnt2[maxn];
bitset<maxn * 60> bs;
vector<int> adj[maxn];
bool vis[maxn];

int getpar(int v)
{
    if(pr[v] == 0)
        return pr[v] = v;
    
    return (v == pr[v] ? v : pr[v] = getpar(pr[v]));
}

bool un(int v, int u)
{
    v = getpar(v);
    u = getpar(u);
    if(u != v)
    {
        pr[u] = v;
        return 1;
    }
    return 0;
}

void dfs(int v = 1, int p = 0, int hi = 1)
{
    vis[v] = 1;
    par[v][0] = p;
    h[v] = hi;
    for(int i = 1; i < maxlog; i++)
        par[v][i] = par[par[v][i - 1]][i - 1];
    
    for(auto u : adj[v])
        if(u != p)
            dfs(u, v, hi + 1);
}

int lca(int v, int u)
{
    if(h[v] < h[u])
        swap(v, u);
    
    for(int i = maxlog - 1; i >= 0; i--)
        if(h[par[v][i]] >= h[u])
            v = par[v][i];
    
    for(int i = maxlog - 1; i >= 0; i--)
        if(par[v][i] != par[u][i])
            u = par[v][i], u = par[u][i];
    
    return (v == u ? v : par[v][0]);
}

void dfs2(int v = 1, int p = 0)
{
    cnt2[v] = cnt[v];
    for(auto u : adj[v])
        if(u != p)
            dfs2(u, v), cnt2[v] += cnt2[u];
}

int main()
{
	ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    cin >> n >> m;

    for(int i = 0; i < m; i++)
    {
        cin >> x >> y;
        if(un(x, y))
        {
            adj[x].pb(y);
            adj[y].pb(x);
            bs[i] = 1;
        }
    }

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

    cin.seekg(0, ios::beg);

    cin >> n >> m;

    for(int i = 0; i < m; i++)
    {
        cin >> x >> y;
        if(bs[i] == 1)
            continue;
        
        //cout << x << " " << y << '\n';
        
        cnt[x] ++;
        cnt[y] ++;
        cnt[lca(x, y)] -= 2;
    }

    //return 0;
    memset(vis, 0, maxn);

    for(int i = 1; i <= n; i++)
        if(!vis[i])
            dfs2(i);

    vector<pair<int, int> > ans;

    for(int i = 2; i <= n; i++)
        if(cnt2[i] == 0&& par[i][0] != 0)
            ans.pb({i, par[i][0]});
    
    cout << ans.size() << '\n';

    for(auto x : ans)
        cout << x.F << " " << 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: 0 / 10
• Subtask 2: 0 / 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