Submission #591987

#	Time	Username	Problem	Language	Result	Execution time	Memory
591987		andrei_boaca	Pipes (CEOI15_pipes)	C++14	50 / 100	4781 ms	32736 KiB

pipes

#include <bits/stdc++.h>

using namespace std;
typedef pair<int,int> pii;
vector<vector<int>> muchii;
int comp[100005],myroot[100005],dp[19][100005],val[100005],par[100005],niv[100005],lg[100005];
set<pii> used;
vector<pii> edges;
int n,m;
int what;
int LCA(int a,int b)
{
    if(niv[a]<niv[b])
        swap(a,b);
    int dif=niv[a]-niv[b];
    for(int i=0;i<=17;i++)
        if((dif>>i)&1)
            a=dp[i][a];
    if(a==b)
        return a;
    for(int i=17;i>=0;i--)
        if(dp[i][a]!=0&&dp[i][b]!=0)
            if(dp[i][a]!=dp[i][b])
            {
                a=dp[i][a];
                b=dp[i][b];
            }
    assert(par[a]==par[b]&&a!=b);
    return par[a];
}
void dfscalc(int nod)
{
    for(int i:muchii[nod])
        if(i!=par[nod])
        {
            dfscalc(i);
            val[nod]+=val[i];
        }
    if(val[nod])
    {
        int a=min(nod,par[nod]);
        int b=max(nod,par[nod]);
        bool ok=0;
        if(a==1&&b==8)
            ok=1;
        used.insert({a,b});
    }
    comp[nod]=what;
}
void dfsbuild(int nod)
{
    val[nod]=0;
    dp[0][nod]=par[nod];
    for(int i=1;i<=17;i++)
        dp[i][nod]=dp[i-1][dp[i-1][nod]];
    for(int i:muchii[nod])
        if(i!=par[nod])
        {
            par[i]=nod;
            niv[i]=niv[nod]+1;
            dfsbuild(i);
        }
}
void dsumerge(int a, int b)
{
    int c1=comp[a],c2=comp[b];
    if(lg[c1]<lg[c2])
    {
        swap(a,b);
        swap(c1,c2);
    }
    what=c1;
    dfscalc(myroot[c2]);
    par[b]=a;
    lg[c1]+=lg[c2];
    lg[c2]=0;
    niv[b]=niv[a]+1;
    muchii[a].push_back(b);
    muchii[b].push_back(a);
    dfsbuild(b);
}
int main()
{
    cin>>n>>m;
    muchii.resize(n+1);
    for(int i=1;i<=n;i++)
    {
        niv[i]=1;
        lg[i]=1;
        comp[i]=i;
        myroot[i]=i;
        par[i]=0;
        val[i]=0;
    }
    int cnt=0;
    for(int z=1;z<=m;z++)
    {
        int a,b;
        cin>>a>>b;
        if(comp[a]!=comp[b])
        {
            cnt++;
            dsumerge(a,b);
            edges.push_back({min(a,b),max(a,b)});
        }
        else
        {
            int lca=LCA(a,b);
            val[a]++;
            val[b]++;
            val[lca]-=2;
        }
    }
    assert(cnt<=n-1);
    for(int i=1;i<=n;i++)
        if(lg[i])
            dfscalc(myroot[i]);
    for(auto i:edges)
        if(used.find(i)==used.end())
            cout<<i.first<<' '<<i.second<<'\n';
    return 0;
}

Compilation message (stderr)

pipes.cpp: In function 'void dfscalc(int)':
pipes.cpp:43:14: warning: variable 'ok' set but not used [-Wunused-but-set-variable]
   43 |         bool ok=0;
      |              ^~

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