Submission #941877

#	Time	Username	Problem	Language	Result	Execution time	Memory
941877		benjaminkleyn	Longest Trip (IOI23_longesttrip)	C++17	85 / 100	12 ms	860 KiB

longesttrip

#include <bits/stdc++.h>
#include "longesttrip.h"
using namespace std;

vector<int> longest_trip(int N, int D)
{
    if (D == 3)
    {
        vector<int> res(N);
        iota(res.begin(), res.end(), 0);
        return res;
    }

    if (D == 2)
    {
        vector<int> res;
        int cur;
        if (are_connected({0}, {1}))
            res = {0, 1}, cur = 2;
        else
            res = {0, 2, 1}, cur = 3;

        for (int i = cur; i < N; i++)
        {
            if (!are_connected({res.back()}, {i}))
                reverse(res.begin(), res.end());
            res.push_back(i);
        }

        return res;
    }

    vector<int> A = {0}, B = {1};
    bool flagAB = false;
    for (int i = 2; i < N; i++)
    {
        if (flagAB || are_connected({i}, {A.back(), B.back()}))
        {
            if (are_connected({i}, {A.back()}))
                A.push_back(i);
            else
            {
                flagAB = true; // we know that there is no edge between A.back() and B.back().
                B.push_back(i);
                continue;
            }
        }
        else
        {
            reverse(B.begin(), B.end());
            for (int x : B)
                A.push_back(x);
            B = {i};
        }
        flagAB = false;
    }
    if (!are_connected(A, B))
    {
        if (A.size() > B.size())
            return A;
        return B;
    }
    if (A.size() > 1 && !are_connected({A[0]}, {A.back()}))
    {
        if ((!flagAB) && are_connected({A.back()}, {B.back()}))
            reverse(A.begin(), A.end());
        for (int x : A)
            B.push_back(x);
        return B;
    }
    if (B.size() > 1 && !are_connected({B[0]}, {B.back()}))
    {
        if ((!flagAB) && are_connected({A.back()}, {B.back()}))
            reverse(B.begin(), B.end());
        for (int x : B)
            A.push_back(x);
        return A;
    }
    int lo = 1, hi = A.size();
    while (lo < hi)
    {
        int mid = (lo + hi) / 2;
        if (are_connected(vector<int>(A.begin(), A.begin() + mid), B))
            hi = mid;
        else
            lo = mid + 1;
    }
    int idxA = lo - 1;
    lo = 1, hi = B.size();
    while (lo < hi)
    {
        int mid = (lo + hi) / 2;
        if (are_connected(vector<int>(B.begin(), B.begin() + mid), {A[idxA]}))
            hi = mid;
        else
            lo = mid + 1;
    }
    int idxB = lo - 1;
    vector<int> res;
    for (int i = idxA + 1; i < A.size(); i++)
        res.push_back(A[i]);
    for (int i = 0; i <= idxA; i++)
        res.push_back(A[i]);
    for (int i = idxB; i < B.size(); i++)
        res.push_back(B[i]);
    for (int i = 0; i < idxB; i++)
        res.push_back(B[i]);
    return res;
}

Compilation message (stderr)

longesttrip.cpp: In function 'std::vector<int> longest_trip(int, int)':
longesttrip.cpp:100:30: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  100 |     for (int i = idxA + 1; i < A.size(); i++)
      |                            ~~^~~~~~~~~~
longesttrip.cpp:104:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  104 |     for (int i = idxB; i < B.size(); i++)
      |                        ~~^~~~~~~~~~

• Subtask 0: 0 / 0
• Subtask 1: 5 / 5
• Subtask 2: 10 / 10
• Subtask 3: 25 / 25
• Subtask 4: 45 / 60