Submission #317466

#	Time	Username	Problem	Language	Result	Execution time	Memory
317466		mohamedsobhi777	Parachute rings (IOI12_rings)	C++14	37 / 100	1927 ms	104280 KiB

rings

#include <bits/stdc++.h>

using namespace std;
int N;
const int cn = 1e6;

vector<int> adj[cn];
int deg[cn];
int vis[cn];
int c;
bool bd = 1;
int del;
vector<int> vec;
set<int> th;
int asy = 1;
int cs = 0;

struct dsu
{
        int fat[cn];
        dsu()
        {
                memset(fat, 0, sizeof fat);
                for (int i = 0; i < cn; ++i)
                        fat[i] = i;
        }
        inline int find(int x) { return fat[x] = (x == fat[x] ? x : find(fat[x])); }
        inline bool same(int x, int y) { return find(x) == find(y); }
        void link(int u, int v)
        {
                u = find(u);
                v = find(v);
                if (fat[u] != v)
                        fat[u] = v;
        }
} d1;

void dfs(int x, int p)
{
        vis[x] = c;
        int ch = (p != x);

        for (auto u : adj[x])
        {
                if (u == p || del == u)
                        continue;
                if (vis[u] == c)
                        bd = 0;
                else
                        dfs(u, x), ++ch;
        }
        if (ch > 2)
                bd = 0;
}
set<int> bigs;

bool check(int i)
{
        del = i;
        for (auto u : adj[i])
        {
                deg[u]--;
                deg[i]--;
        }
        bool ok = 1;

        for (int j = 0; j < N; ++j)
        {
                ++c;
                if (vis[j] != c && i != j)
                {
                        bd = 1;
                        dfs(j, j);
                        ok &= bd;
                }
        }

        for (auto u : adj[i])
        {
                deg[u]++;
                deg[i]++;
        }
        return ok;
}

vector<int> cyc;
vector<int> now;
int onc[cn];

void detect(int x, int p)
{
        if (vis[x] == c)
        {
                cyc = now;
                for (auto u : now)
                        onc[u] = 1;
                return;
        }
        now.push_back(x);

        vis[x] = c;
        for (auto u : adj[x])
        {
                if (u == p || (int)cyc.size())
                        continue;
                detect(u, x);
        }
        now.pop_back();
}

int brute()
{
        int ret = 0;
        set<int> uni;

        if (cs > 1 || bigs.size() > 1 || th.size() > 2)
                return 0;
        if (th.size() == 0 && asy)
                return N;
        if (cs == 1 && th.size() == 0)
                return (int)cyc.size();
        if (bigs.size())
        {
                if (asy)
                        return 1;
                return onc[*bigs.begin()];
        }
        int ans1 = 0;
        if (th.size() == 1)
        {
                if (asy)
                        return 1 + (int)adj[*th.begin()].size();
                ++c;
                set<int> anss;
                int a = (*th.begin());
                if (check(a))
                {
                        anss.insert(a);
                }
                for (auto u : adj[a])
                {
                        ++c;
                        if (check(u))
                                anss.insert(u);
                }
                ans1 = (int)anss.size();
                //                return (int)anss.size();
        }
        else if (th.size() == 2)
        {

                int a = *th.begin();
                int b = *th.rbegin();
                if (cs)
                {
                        if (onc[a] + onc[b] == 0)
                                return 0;
                }
                map<int, int> mp;
                for (auto u : adj[a])
                        mp[u]++;
                for (auto u : adj[b])
                        mp[u]++;
                mp[a]++;
                mp[b]++;
                for (auto u : mp)
                {
                        if ((onc[u.first] || !cs) && u.second == 2)
                                ++ret;
                }
                return ret;
        }
        set<int> ass;
        if (th.size() == 0)
                return N;
        else
        {
                for (auto u : adj[*th.begin()])
                        ass.insert(u);
                ass.insert(*th.begin());
        }
        assert(th.size() == 1);
        for (auto i : ass)
        {
                ++c;
                if (check(i))
                {
                        if (th.size())
                                assert(ass.find(i) != ass.end());
                        ++ret;
                }
        }
        if (th.size())
        {
                assert(ret == ans1);
        }
        return ret;
}

void Init(int N_)
{

        N = N_;
}
void Link(int A, int B)
{
        adj[A].push_back(B);
        adj[B].push_back(A);
        cs += (d1.same(A, B));
        if (d1.same(A, B) && asy)
        {
                ++c;
                detect(A, A);
                asy = 0;
        }

        d1.link(A, B);
        deg[A]++;
        deg[B]++;
        if (deg[A] > 3)
                bigs.insert(A);
        if (deg[B] > 3)
                bigs.insert(B);
        if (deg[A] == 3)
        {
                th.insert(A);
        }
        if (deg[B] == 3)
        {
                th.insert(B);
        }
}

int CountCritical()
{
        if (bigs.size() > 1)
                return 0;
        return brute();
        return N;
}

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