Submission #858952

#	Time	Username	Problem	Language	Result	Execution time	Memory
858952		Tenis0206	Pipes (CEOI15_pipes)	C++11	100 / 100	1644 ms	15524 KiB

pipes

#include <bits/stdc++.h>

using namespace std;

const int nmax = 1e5;

int n,m;

int td[nmax + 5], rang[nmax + 5];

int lvl[nmax + 5], t[nmax + 5][17];

int sum[nmax + 5];

pair<int,int> e[nmax + 5];

vector<pair<int,int>> G[nmax + 5];

bitset<nmax + 5> ok;

int nre = 0;

int rep(int x)
{
    if(x==td[x])
    {
        return x;
    }
    return (td[x] = rep(td[x]));
}

int lca(int x, int y)
{
    if(lvl[x] > lvl[y])
    {
        swap(x,y);
    }
    int dif = lvl[y] - lvl[x];
    for(int p=0; p<=16; p++)
    {
        if((dif & (1<<p))!=0)
        {
            y = t[y][p];
        }
    }
    if(x==y)
    {
        return x;
    }
    for(int p=16; p>=0; p--)
    {
        if(t[x][p] && t[y][p] && t[x][p]!=t[y][p])
        {
            x = t[x][p];
            y = t[y][p];
        }
    }
    return t[x][0];
}

void update(int x, int y)
{
    int l = lca(x,y);
    ++sum[x];
    --sum[l];
    ++sum[y];
    --sum[l];
}

void get_ans(int nod, int dad = 0)
{
    for(auto it : G[nod])
    {
        if(it.first==dad)
        {
            continue;
        }
        get_ans(it.first,nod);
        sum[nod] += sum[it.first];
        if(sum[it.first] > 0)
        {
            ok[it.second] = 1;
        }
    }
}

void dfs_dad(int nod, int dad, int level)
{
    lvl[nod] = level;
    t[nod][0] = dad;
    for(int p=1; p<=16; p++)
    {
        t[nod][p] = t[t[nod][p-1]][p-1];
    }
    sum[nod] = 0;
    for(auto it : G[nod])
    {
        if(it.first==dad)
        {
            continue;
        }
        dfs_dad(it.first,nod,level + 1);
    }
}

int get_root(int nod)
{
    while(t[nod][0])
    {
        nod = t[nod][0];
    }
    return nod;
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
#ifdef home
    freopen("nr.in","r",stdin);
    freopen("nr.out","w",stdout);
#endif // home
    cin>>n>>m;
    for(int i=1; i<=n; i++)
    {
        rang[i] = 1;
        td[i] = i;
    }
    for(int i=1; i<=m; i++)
    {
        int x,y;
        cin>>x>>y;
        if(rep(x) == rep(y))
        {
            update(x,y);
            continue;
        }
        e[++nre] = {x,y};
        int rx = rep(x);
        int ry = rep(y);
        if(rang[ry] > rang[rx])
        {
            swap(rx,ry);
            swap(x,y);
        }
        td[ry] = rx;
        rang[rx] += rang[ry];
        int r = get_root(y);
        get_ans(r);
        G[x].push_back({y,nre});
        G[y].push_back({x,nre});
        dfs_dad(y,x,lvl[x] + 1);
    }
    get_ans(get_root(1));
    for(int i=1; i<=nre; i++)
    {
        int x = e[i].first, y = e[i].second;
        if(ok[i]==0)
        {
            cout<<x<<' '<<y<<'\n';
        }
    }
    return 0;
}

• 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