Submission #1010782

#	Time	Username	Problem	Language	Result	Execution time	Memory
1010782		GrindMachine	Thousands Islands (IOI22_islands)	C++17	1.75 / 100	24 ms	10200 KiB

islands

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

template<typename T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef long long int ll;
typedef long double ld;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;

#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL)
#define pb push_back
#define endl '\n'
#define sz(a) (int)a.size()
#define setbits(x) __builtin_popcountll(x)
#define ff first
#define ss second
#define conts continue
#define ceil2(x,y) ((x+y-1)/(y))
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define yes cout << "Yes" << endl
#define no cout << "No" << endl

#define rep(i,n) for(int i = 0; i < n; ++i)
#define rep1(i,n) for(int i = 1; i <= n; ++i)
#define rev(i,s,e) for(int i = s; i >= e; --i)
#define trav(i,a) for(auto &i : a)

template<typename T>
void amin(T &a, T b) {
    a = min(a,b);
}

template<typename T>
void amax(T &a, T b) {
    a = max(a,b);
}

#ifdef LOCAL
#include "debug.h"
#else
#define debug(...) 42
#endif

/*



*/

const int MOD = 1e9 + 7;
const int N = 1e5 + 5;
const int inf1 = int(1e9) + 5;
const ll inf2 = ll(1e18) + 5;

#include "islands.h"

vector<pii> adj[N];
vector<bool> vis(N), recstack(N);
bool cyc = false;

void dfs1(int u){
    vis[u] = 1;
    recstack[u] = 1;

    for(auto [v,id] : adj[u]){
        if(vis[v]){
            if(recstack[v]){
                cyc = true;
            }
        }
        else{
            dfs1(v);
        }
    }

    recstack[u] = 0;
}

bool line = true;
vector<pii> par(N,{-1,-1});
vector<bool> good(N);

void dfs2(int u, int p){
    vis[u] = 1;
    int d = sz(adj[u])-(p != -1);
    if(d >= 2){
        good[u] = 1;
        line = false;
    }

    for(auto [v,id] : adj[u]){
        if(v == p or vis[v]) conts;
        par[v] = {u,id};
        dfs2(v,u);
    }
}

std::variant<bool, std::vector<int>> find_journey(
    int n, int m, std::vector<int> U, std::vector<int> V) {

    for(int i = 0; i < m; i += 2){
        int u = U[i], v = V[i];
        adj[u].pb({v,i}), adj[v].pb({u,i+1});
    }

    dfs2(0,-1);
    if(line){
        return false;
    }

    vector<int> ans;
    rep(i,n){
        if(!good[i]) conts;
        bool ok = true;
        int u = i;
        vector<int> edges;

        while(true){
            auto [p,pid] = par[u];
            if(p == -1) break;
            edges.pb(pid);
            u = p;
            if(good[u]){
                ok = false;
                break;
            }
        }

        if(!ok) conts;

        vector<int> seq;
        vector<int> v1;

        for(auto [v,id] : adj[i]){
            if(count(all(edges),id^1)) conts;
            v1.pb(id);
        }

        assert(sz(v1) >= 2);
        while(sz(v1) > 2) v1.pop_back();

        int x = v1[0], y = v1[1];
        seq = {x,x^1,y,y^1,x^1,x,y^1,y};
        
        // trav(x,v1) cout << x << " ";
        // cout << endl;
        // trav(x,v2) cout << x << " ";
        // cout << endl;
        // return true;

        // rep(iter,3){
        //     int x = v1[0];
        //     v1.erase(v1.begin());
        //     v2.pb(x);
        //     int y = v2[0];
        //     v2.erase(v2.begin());
        //     v1.pb(y);
        //     seq.pb(x), seq.pb(y);            
        // }

        ans = edges;
        reverse(all(ans));
        trav(x,seq) ans.pb(x);
        trav(x,edges) ans.pb(x);
        
        rep(j,sz(ans)-1) assert(ans[i] != ans[i+1]);
        return ans;
    }

    return true;
}

• Subtask 1: 0 / 5
• Subtask 2: 1.75 / 5
• Subtask 3: 0 / 21
• Subtask 4: 0 / 24
• Subtask 5: 0 / 45