Submission #1242819

#	Time	Username	Problem	Language	Result	Execution time	Memory
1242819		Zbyszek99	Thousands Islands (IOI22_islands)	C++20	100 / 100	66 ms	18724 KiB

islands

#include "islands.h"
#include <bits/stdc++.h>
#define ll long long
#define ld long double
#define ull unsigned long long
#define ff first
#define ss second
#define pii pair<int,int>
#define pll pair<long long, long long>
#define vi vector<int>
#define vl vector<long long>
#define pb push_back
#define rep(i, b) for(int i = 0; i < (b); ++i)
#define rep2(i,a,b) for(int i = a; i <= (b); ++i)
#define rep3(i,a,b,c) for(int i = a; i <= (b); i+=c)
#define count_bits(x) __builtin_popcountll((x))
#define all(x) (x).begin(),(x).end()
#define siz(x) (int)(x).size()
#define forall(it,x) for(auto& it:(x))
using namespace std;
const int INF = 1e9+50;
const ll INF_L = 1e18+40;
const ll MOD = 1e9+7;

int out_deg[100001];
vi in_graph[100001];
bool del[100001];
vector<pii> out_graph[100001];
queue<int> events;
vi ans;
int beg_path_siz = 0;
bool odw[100001];
bool in_cycle[200001];
pii edge[200001];

void del_vert(int x)
{
    del[x] = 1;
    forall(it,in_graph[x])
    {
        out_deg[it]--;
        if(out_deg[it] == 0) events.push(it);
    }
}

int new_beg(int v)
{
    int v2 = -1;
    forall(it,out_graph[v])
    {
        if(del[it.ff]) continue;
        v2 = it.ff;
        beg_path_siz++;
        ans.pb(it.ss);
    }
    del_vert(v);
    return v2;
}

pair<vi,vi> find_cycle(int v, int beg, int beg_edge, int n)
{
    vi ans2 = {beg_edge};
    rep(i,n) odw[i] = 0;
    odw[beg] = 1;
    while(odw[v] == 0)
    {
        ans2.pb(out_graph[v][0].ss);
        odw[v] = 1;
        v = out_graph[v][0].ff;
    }
    vi cycle = {ans2.back()};
    vi path = {};
    for(int i = siz(ans2)-2; i >= 0; i--)
    {
        cycle.pb(ans2[i]);
        if(edge[ans2[i]].ff == v)
        {
            for(int j = 0; j < i; j++) path.pb(ans2[j]);
            break;
        }
    }
    reverse(all(cycle));
    return {path,cycle};
}

variant<bool,vi> find_journey(int n, int m, vi u, vi v) 
//vi find_journey(int n, int m, vi u, vi v)
{
    rep(i,m)
    {
        edge[i] = {u[i],v[i]};
        out_graph[u[i]].pb({v[i],i});
    }
    rep(i,m)
    {
        out_deg[u[i]]++;
        in_graph[v[i]].pb(u[i]);
    }
    rep(i,n)
    {
        if(out_deg[i] == 0) events.push(i);
    }
    int cur_beg = 0;
    while(out_deg[cur_beg] <= 1)
    {
        int nb = new_beg(cur_beg);
        if(nb == -1) return (bool)0;
        cur_beg = nb;
    }
    while(!events.empty())
    {
        int x = events.front();
        events.pop();
        if(del[x]) continue;
        del_vert(x);
        while(out_deg[cur_beg] <= 1)
        {
            int nb = new_beg(cur_beg);
            if(nb == -1) return (bool)0;
            cur_beg = nb;
        }
    }
    rep(i,n) out_graph[i] = {};
    rep(i,m)
    {
        if(del[u[i]] || del[v[i]]) continue;
        out_graph[u[i]].pb({v[i],i});
    }
    pair<vi,vi> cycle1 = find_cycle(out_graph[cur_beg][0].ff,cur_beg,out_graph[cur_beg][0].ss,n);
    pair<vi,vi> cycle2 = find_cycle(out_graph[cur_beg][1].ff,cur_beg,out_graph[cur_beg][1].ss,n);
    forall(it,cycle1.ss) in_cycle[it] = 1;
    bool is_case = 0;
    forall(it,cycle2.ss) if(in_cycle[it]) is_case = 1;
    if(is_case)
    {
        forall(it,cycle1.ff) ans.pb(it);
        forall(it,cycle1.ss) ans.pb(it);
        reverse(all(cycle1.ff));
        forall(it,cycle1.ff) ans.pb(it);
        vi path = cycle2.ff;
        if(siz(cycle2.ff) == 0)
        {
            rep(i,siz(cycle2.ss))
            {
                if(in_cycle[cycle2.ss[i]]) break;
                path.pb(cycle2.ss[i]);
            }
        }
        forall(it,path) ans.pb(it);
        int beg_edge;
        rep(i,siz(cycle1.ss))
        {
            int it = cycle1.ss[i];
            if(edge[it].ff == edge[path.back()].ss)
            {
                beg_edge = i;
            }
        }
        int cnt = siz(cycle1.ss);
        vi new_cycle;
        while(cnt--)
        {
            new_cycle.pb(cycle1.ss[beg_edge]);
            beg_edge++;
            beg_edge %= siz(cycle1.ss);
        }
        reverse(all(new_cycle));
        forall(it,new_cycle) ans.pb(it);
        reverse(all(path));
        forall(it,path) ans.pb(it);
    }
    else
    {
        forall(it,cycle1.ff) ans.pb(it);
        forall(it,cycle1.ss) ans.pb(it);
        reverse(all(cycle1.ff));
        forall(it,cycle1.ff) ans.pb(it);
        reverse(all(cycle1.ff));

        forall(it,cycle2.ff) ans.pb(it);
        forall(it,cycle2.ss) ans.pb(it);
        reverse(all(cycle2.ff));
        forall(it,cycle2.ff) ans.pb(it);
        reverse(all(cycle2.ff));

        forall(it,cycle1.ff) ans.pb(it);
        reverse(all(cycle1.ss));
        forall(it,cycle1.ss) ans.pb(it);
        reverse(all(cycle1.ff));
        forall(it,cycle1.ff) ans.pb(it);
        reverse(all(cycle1.ff));

        forall(it,cycle2.ff) ans.pb(it);
        reverse(all(cycle2.ss));
        forall(it,cycle2.ss) ans.pb(it);
        reverse(all(cycle2.ff));
        forall(it,cycle2.ff) ans.pb(it);
        reverse(all(cycle2.ff));
    }
    for(int i = beg_path_siz-1; i >= 0; i--)
    {
        ans.pb(ans[i]);
    }
    return ans;
}

• Subtask 1: 5 / 5
• Subtask 2: 5 / 5
• Subtask 3: 21 / 21
• Subtask 4: 24 / 24
• Subtask 5: 45 / 45