Submission #941912

#	Time	Username	Problem	Language	Result	Execution time	Memory
941912		benjaminkleyn	Longest Trip (IOI23_longesttrip)	C++17	100 / 100	13 ms	952 KiB

longesttrip

#include <bits/stdc++.h>
#include "longesttrip.h"
using namespace std;
 
#define all(x) x.begin(), x.end()
#define vi vector<int>
#define C are_connected
#define pb push_back
#define bk back
#define rev(x) reverse(all(x))
 
vi longest_trip(int N, int D)
{
    if (D == 3)
    {
        vi r(N);
        iota(all(r), 0);
        return r;
    }
 
    if (D == 2)
    {
        vi r;
        int t;
        if (C({0}, {1}))
            r = {0, 1}, t = 2;
        else
            r = {0, 2, 1}, t = 3;
 
        for (int i = t; i < N; i++)
        {
            if (!C({r.bk()}, {i}))
                rev(r);
            r.pb(i);
        }
 
        return r;
    }
 
    vi A = {0}, B = {1};
    for (int i = 2; i + 1 < N; i += 2)
    {
        if (C({i}, {i + 1}))
        {
            if (C({i}, {A.bk(), B.bk()}))
            {
                if (C({i}, {A.bk()}))
                {
                    A.pb(i);
                    A.pb(i + 1);
                }
                else
                {
                    B.pb(i);
                    B.pb(i + 1);
                }
            }
            else
            {
                rev(B);
                for (int x : B) A.pb(x);
                B = {i, i + 1};
            }
        }
        else
        {
            if (C({A.bk()}, {i}))
            {
                A.pb(i);
                if (C({B.bk()}, {i + 1}))
                    B.pb(i + 1);
                else
                {
                    rev(B);
                    for (int x : B)
                        A.pb(x);
                    B = {i + 1};
                }
            }
            else
            {
                A.pb(i + 1);
                if (C({B.bk()}, {i}))
                    B.pb(i);
                else
                {
                    rev(B);
                    for (int x : B)
                        A.pb(x);
                    B = {i};
                }
            }
        }
    }
    if (N % 2)
    {
        if (C({N - 1}, {A.bk(), B.bk()}))
        {
            if (C({N - 1}, {A.bk()}))
                A.pb(N - 1);
            else
                B.pb(N - 1);
        }
        else
        {
            rev(B);
            for (int x : B)
                A.pb(x);
            B = {N - 1};
        }
    }
    if (!C(A, B))
    {
        if (A.size() > B.size())
            return A;
        return B;
    }
    if (A.size() > 1 && !C({A[0]}, {A.bk()}))
    {
        if (C({A.bk()}, {B.bk()}))
            rev(A);
        for (int x : A)
            B.pb(x);
        return B;
    }
    if (B.size() > 1 && !C({B[0]}, {B.bk()}))
    {
        if (C({A.bk()}, {B.bk()}))
            rev(B);
        for (int x : B)
            A.pb(x);
        return A;
    }

    auto s = [](vi X, vi Y)
    {
        int a = 1, b = X.size();
        while (a < b)
        {
            int m = (a + b) / 2;
            if (C(vi(X.begin(), X.begin() + m), Y))
                b = m;
            else
                a = m + 1;
        }
        return a - 1;
    };
    int x = s(A, B);
    int y = s(B, {A[x]});
    vi r;
    for (int i = x + 1; i <= x + A.size(); i++)
        r.pb(A[i % A.size()]);
    for (int i = y; i < y + B.size(); i++)
        r.pb(B[i % B.size()]);
    return r;
}

Compilation message (stderr)

longesttrip.cpp: In function 'std::vector<int> longest_trip(int, int)':
longesttrip.cpp:151:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  151 |     for (int i = x + 1; i <= x + A.size(); i++)
      |                         ~~^~~~~~~~~~~~~~~
longesttrip.cpp:153:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  153 |     for (int i = y; i < y + B.size(); i++)
      |                     ~~^~~~~~~~~~~~~~

• Subtask 0: 0 / 0
• Subtask 1: 5 / 5
• Subtask 2: 10 / 10
• Subtask 3: 25 / 25
• Subtask 4: 60 / 60