Submission #1071923

#	Time	Username	Problem	Language	Result	Execution time	Memory
1071923		c2zi6	Thousands Islands (IOI22_islands)	C++17	6.75 / 100	26 ms	8540 KiB

islands

#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
#define ff first
#define ss second
#define pb push_back
#define all(a) (a).begin(), (a).end()
#define replr(i, a, b) for (int i = int(a); i <= int(b); ++i)
#define reprl(i, a, b) for (int i = int(a); i >= int(b); --i)
#define rep(i, n) for (int i = 0; i < int(n); ++i)
#define mkp(a, b) make_pair(a, b)
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> PII;
typedef vector<int> VI;
typedef vector<PII> VPI;
typedef vector<VI> VVI;
typedef vector<VVI> VVVI;
typedef vector<VPI> VVPI;
typedef pair<ll, ll> PLL;
typedef vector<ll> VL;
typedef vector<PLL> VPL;
typedef vector<VL> VVL;
typedef vector<VVL> VVVL;
typedef vector<VPL> VVPL;
template<class T> T setmax(T& a, T b) {if (a < b) return a = b; return a;}
template<class T> T setmin(T& a, T b) {if (a < b) return a; return a = b;}
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
template<class T>
using indset = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
#include "islands.h"

namespace GETPATH {
    VI vis;
    VVPI gp;
    VI order;
    bool dfs(int u, int e) {
        if (u == e) return true;
        while (gp[u].size()) {
            auto[v, i] = gp[u].back();
            gp[u].pop_back();
            if (vis[i]) continue;
            vis[i] = true;
            order.pb(i);
            if (dfs(v, e)) return true;
            order.pop_back();
        }
        return false;
    }
};

int n, m;
VVPI gp;
VI getpath(int s, int e, VI exclude) {
    GETPATH::vis = VI(m);
    for (int x : exclude) GETPATH::vis[x] = true;
    GETPATH::gp = gp;
    GETPATH::order = VI();
    if (GETPATH::dfs(s, e)) return GETPATH::order;
    return {};
}

VI reverse(VI a) {
    reverse(all(a));
    return a;
}

VI vis;
VVPI undirgp;
bool cyclecheck(int u, int pi = -1) {
    vis[u] = true;
    for (auto[v, i] : undirgp[u]) if (i != pi) {
        if (vis[v]) return true;
        if (cyclecheck(v, i)) return true;
    }
    return false;
}

variant<bool, VI> find_journey(int N, int M, VI U, VI V) {
    n = N;
    m = M;
    gp = VVPI(n);

    undirgp = VVPI(n);
    rep(i, m) {
        gp[U[i]].pb({V[i], i});

        undirgp[U[i]].pb({V[i], i/2});
    }
    if (N == 2) {
        if (gp[0].size() < 2 || gp[1].size() < 1) return false;
        VI ans;
        ans.pb(gp[0][0].ss);
        ans.pb(gp[1][0].ss);
        ans.pb(gp[0][1].ss);
        ans.pb(gp[0][0].ss);
        ans.pb(gp[1][0].ss);
        ans.pb(gp[0][1].ss);
        return ans;
    }

    vis = VI(n);
    if (cyclecheck(0)) {
        return true;
        return VI{1, 4, 8, 8};
    }
    return false;

    for (auto[v, i] : gp[0]) {
        VI ret = getpath(0, v, {i});
        if (ret.size() == 0) continue;
        int het = -1;
        for (auto[u, i] : gp[v]) if (u == 0) het = i;
        if (het == -1) continue;

        VI ans;
        for (int x : ret) ans.pb(x);
        ans.pb(het);
        ans.pb(i);
        for (int x : reverse(ret)) ans.pb(x);
        ans.pb(het);
        ans.pb(i);
        return ans;
    }

    return false;
}

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