Submission #1010512

#	Time	Username	Problem	Language	Result	Execution time	Memory
1010512		GrindMachine	Thousands Islands (IOI22_islands)	C++17	1.75 / 100	27 ms	7856 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"

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

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

    trav(v,adj[u]){
        if(vis[v]){
            if(recstack[v]){
                cyc = true;
            }
        }
        else{
            dfs1(v);
        }
    }

    recstack[u] = 0;
}

struct DSU {
    vector<int> par, rankk, siz;
    vector<int> bad;

    DSU() {

    }

    DSU(int n) {
        init(n);
    }

    void init(int n) {
        par = vector<int>(n + 1);
        rankk = vector<int>(n + 1);
        siz = vector<int>(n + 1);
        bad = vector<int>(n + 1);
        rep(i, n + 1) create(i);
    }

    void create(int u) {
        par[u] = u;
        rankk[u] = 0;
        siz[u] = 1;
    }

    int find(int u) {
        if (u == par[u]) return u;
        else return par[u] = find(par[u]);
    }

    bool same(int u, int v) {
        return find(u) == find(v);
    }

    void merge(int u, int v) {
        u = find(u), v = find(v);
        if (u == v){
            bad[u] = 1;
            return;
        }

        if (rankk[u] == rankk[v]) rankk[u]++;
        if (rankk[u] < rankk[v]) swap(u, v);

        par[v] = u;
        siz[u] += siz[v];
        bad[u] |= bad[v];
    }
};

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

    DSU dsu(n);
    int deg = 0;

    for(int i = 0; i < m; i += 2){
        int u = U[i], v = V[i];
        dsu.merge(u,v);
        if(u == 0 or v == 0) deg++;
    }

    int p = dsu.find(0);
    return (bool)(dsu.bad[p]|(dsu.siz[p] > deg+1));

    // if (n == 4) {
    //     return std::vector<int>({0, 1, 2, 4, 0, 3, 2, 1, 4, 3});
    // }

    // return false;
}

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