Submission #596097

#	Time	Username	Problem	Language	Result	Execution time	Memory
596097		Bench0310	Parachute rings (IOI12_rings)	C++17	37 / 100	1076 ms	77712 KiB

rings

#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

const int N=1000000;
int n;
vector<int> v[N];
int deg[N];
int bad=0;
int big[N]; //number of adjacent big nodes
int cnt[N+1]; //number of good nodes with i adjacent big nodes
int cntbad[N+1]; //number of bad nodes with i adjacent big nodes
vector<int> four;
int p[N];
int sz[N];
vector<array<int,2>> cycle_edges;
int incycle[N];
bool valid[N];

int find_set(int a)
{
    if(a==p[a]) return a;
    else return p[a]=find_set(p[a]);
}

bool merge_sets(int a,int b)
{
    a=find_set(a);
    b=find_set(b);
    if(a==b) return 0;
    if(sz[a]<sz[b]) swap(a,b);
    p[b]=a;
    sz[a]+=sz[b];
    return 1;
}

vector<int> find_path(int a,int b)
{
    vector<int> u(n,-1);
    u[a]=-2;
    queue<int> q;
    q.push(a);
    while(!q.empty())
    {
        int e=q.front();
        q.pop();
        for(int to:v[e])
        {
            if(u[to]==-1)
            {
                u[to]=e;
                q.push(to);
            }
        }
    }
    vector<int> path={b};
    while(path.back()!=a) path.push_back(u[path.back()]);
    for(int x:path) incycle[x]++;
    return path;
}

void Init(int _n)
{
    n=_n;
    cnt[0]=n;
    for(int i=0;i<n;i++)
    {
        p[i]=i;
        sz[i]=1;
        valid[i]=1;
    }
}

void upd(int a,int d)
{
    if(valid[a]) (deg[a]<=2?cnt[big[a]]:cntbad[big[a]])+=d;
}

void updbig(int a)
{
    upd(a,-1);
    big[a]++;
    upd(a,1);
}

void upddeg(int a)
{
    upd(a,-1);
    deg[a]++;
    upd(a,1);
    if(deg[a]==3)
    {
        bad++;
        for(int to:v[a]) updbig(to);
    }
    if(deg[a]==4) four.push_back(a);
}

void new_valid(vector<int> opt)
{
    vector<int> now(n,0);
    for(int a:opt) now[a]=1;
    for(int i=0;i<n;i++)
    {
        if(valid[i]&&!now[i])
        {
            upd(i,-1);
            valid[i]=0;
        }
    }
}

void Link(int a, int b)
{
    if(merge_sets(a,b)==1)
    {
        v[a].push_back(b);
        v[b].push_back(a);
    }
    else
    {
        cycle_edges.push_back({a,b});
        if(cycle_edges.size()==1) new_valid(find_path(a,b));
        else if(cycle_edges.size()==2)
        {
            vector<int> path=find_path(a,b);
            vector<int> opt;
            for(int x:path)
            {
                int c=0;
                for(int to:v[x]) c+=(incycle[to]==2);
                if(incycle[x]==2&&c<=1) opt.push_back(x);
            }
            new_valid(opt);
        }
        else if(cycle_edges.size()==3) new_valid({});
    }
    upddeg(a);
    upddeg(b);
}

int CountCritical()
{
    if(four.size()==0) return cnt[bad]+cntbad[bad-1];
    else if(four.size()==1) return (valid[four[0]]&&big[four[0]]==bad-1);
    else return 0;
}

• Subtask 1: 20 / 20
• Subtask 2: 17 / 17
• Subtask 3: 0 / 18
• Subtask 4: 0 / 14
• Subtask 5: 0 / 31