Submission #730237

#	Time	Username	Problem	Language	Result	Execution time	Memory
730237		Nahian9696	Thousands Islands (IOI22_islands)	C++17	5 / 100	34 ms	4432 KiB

islands

#include "islands.h"

#include <variant>
#include <vector>
#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vll;


#define f0(i, n) for(int i = 0; i <  (n); i++)
#define f1(i, n) for(int i = 1; i <= (n); i++)
#define ff first
#define ss second
#define pb push_back

int opp(int n) {
    if(n % 2 == 0) return n+1;
    return n-1;
}

std::variant<bool, std::vector<int>> find_journey(
    int N, int M, std::vector<int> U, std::vector<int> V) {

    if(N == 2) {
        vi zr, on;
        f0(i, M) {
            if(U[i] == 0) zr.pb(i);
            else on.pb(i);
        }
        if(zr.size() < 2 || on.size() < 1) return false;
        return vi({zr[0], on[0], zr[1], zr[0], on[0], zr[1]});
    }

    bool sbtsk3 = (M % 2 == 0);
    bool sbtsk4 = (M % 2 == 0);

    f0(i, M - 1) {
        if(i % 2 == 0) {
            if(U[i] != V[i+1] || V[i] != U[i+1]) {
                sbtsk3 = false;
            }
            if(U[i] != U[i+1] || V[i] != V[i+1]) {
                sbtsk4 = false;
            }
        }
    }


    if(sbtsk3) {
        vector<pair<int, int>> grph[N];
        bool vis[N] = {0};
        f0(i, M) {
            grph[U[i]].pb({V[i], i});
        }
        vi ans, t_ans;

        int cur = 0;
        vis[cur] = true;

        if(grph[cur].size() > 1) {
            int x = grph[cur][0].ss, y = grph[cur][1].ss;
            return vi({x, opp(x), y, opp(y), opp(x), x, opp(y), y});
        } else {
            ans.pb(grph[cur][0].ss);
            cur = grph[cur][0].ff;
        }

        vis[cur] = true;

        while(grph[cur].size() <= 2) {
            if(grph[cur].size() == 1) return false;

            for(auto nxt: grph[cur]) {
                if(!vis[nxt.ff]) {
                    ans.pb(nxt.ss);
                    cur = nxt.ff;
                    vis[cur] = true;
                }
            }
        }

        for(auto nxt: grph[cur]) {
            if(!vis[nxt.ff]) {
                t_ans.pb(nxt.ss);
            }
        }
        int x = t_ans[0], y = t_ans[1];
        t_ans.clear();
        t_ans = vi(ans.rbegin(), ans.rend());

        ans.pb(x);
        ans.pb(opp(x));
        ans.pb(y);
        ans.pb(opp(y));
        ans.pb(opp(x));
        ans.pb(x);
        ans.pb(opp(y));
        ans.pb(y);

        for(int e: t_ans) ans.pb(e);

        return ans;
    }








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

Compilation message (stderr)

islands.cpp: In function 'std::variant<bool, std::vector<int, std::allocator<int> > > find_journey(int, int, std::vector<int>, std::vector<int>)':
islands.cpp:39:10: warning: variable 'sbtsk4' set but not used [-Wunused-but-set-variable]
   39 |     bool sbtsk4 = (M % 2 == 0);
      |          ^~~~~~

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