Submission #689602

#	Time	Username	Problem	Language	Result	Execution time	Memory
689602		LucaLucaM	Table Tennis (info1cup20_tabletennis)	C++17	100 / 100	156 ms	4688 KiB

tabletennis

#include <bits/stdc++.h>

using namespace std;

/**
trebuie sa alegem n din n + k numere astfel incat
a[1] + a[n] = a[2] + a[n-1] = ... = a[n/2] + a[n/2+1]
a[1] + a[n] = a[2] + a[n-1]
a[n] - a[n-1] = a[2] - a[1]
a[n-1] - a[n-2] = a[3] - a[2]
...
a[n/2+1] - a[n/2] = a[n] - a[n-1]

n*k + nlogn?
**/

int a[150401];

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);

    int n, k;
    cin >> n >> k;

    int m = n + k;

    for (int i=1; i<=m; i++)
        cin >> a[i];

    for (int i=1; i<=k+1; i++) /// O(k)
    {
        /// incercam sa fie a[i] cel mai mic element , a[j] cel mai mare

        for (int j=m; m-j+i-1 <= k; j--) /// O(k*k)
        {
            int sum = a[i] + a[j];
            int l=i, r=j;

            int cnt = 0;

            while (l < r)
            {
                while (l < r && a[l] + a[r] > sum)
                    r--;
                while (l < r && a[l] + a[r] < sum)
                    l++;
                if (a[l] + a[r] != sum)
                {
                    cnt = -1;
                    break;
                }
                cnt++;
                l++;
            }

            if (cnt >= n/2)
            {
                cnt = n / 2;
                vector<int>ans;
                int l=i, r=j;
                while (l < r && cnt--)
                {
                    while (l < r && a[l] + a[r] > sum)
                        r--;
                    while (l < r && a[l] + a[r] < sum)
                        l++;
                    ans.push_back(a[l]);
                    ans.push_back(a[r]);
                    l++, r--;
                }

                for (int i=0; i<n; i+=2)
                    cout << ans[i] << ' ';
                reverse(ans.begin(), ans.end());
                for (int i=int(ans.size()) & 1; i<ans.size(); i+=2)
                    cout << ans[i] << ' ';

                return 0;
            }
        }
    }

    return 0;
}

Compilation message (stderr)

tabletennis.cpp: In function 'int main()':
tabletennis.cpp:78:50: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   78 |                 for (int i=int(ans.size()) & 1; i<ans.size(); i+=2)
      |                                                 ~^~~~~~~~~~~

• Subtask 1: 11 / 11
• Subtask 2: 9 / 9
• Subtask 3: 14 / 14
• Subtask 4: 15 / 15
• Subtask 5: 9 / 9
• Subtask 6: 14 / 14
• Subtask 7: 15 / 15
• Subtask 8: 13 / 13