Submission #675226

#	Time	Username	Problem	Language	Result	Execution time	Memory
675226		vjudge1	Table Tennis (info1cup20_tabletennis)	C++17	100 / 100	198 ms	4324 KiB

tabletennis

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
vector<int> a;
vector<pair<int, int>> solve(int sum){
    vector<pair<int, int>> result;
    for (int lptr=0, rptr=a.size()-1; lptr < rptr;){
        int csum = a[lptr] + a[rptr];
        if (csum == sum){
            result.emplace_back(a[lptr++], a[rptr--]);
        }
        else if (csum > sum){
            rptr--;
        }
        else{
            lptr++;
        }
    }
    return result;
}
bool solvable(int n, int sum){
    int left = a.size();
    for (int lptr=0, rptr=a.size()-1; lptr < rptr;){
        int csum = a[lptr] + a[rptr];
        if (csum == sum){
            lptr++, rptr--;
            n -= 2;
            left -= 2;
        }
        else if (csum > sum){
            rptr--;
            left--;
        }
        else{
            lptr++;
            left--;
        }
        if (n == 0) return true;
        if (left < n) return false;
    }
    return false;
}
mt19937 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
signed main(){
    cin.tie(0)->sync_with_stdio(0);
    int n, k; cin >> n >> k;
    a.resize(n+k);
    for (int i=0; i<a.size(); i++) cin >> a[i];
    sort(a.begin(), a.end());
    vector<int> possible_sums;
    for (int i=0; i<=k; i++){
        for (int j=0; j+i<=k; j++){
            possible_sums.push_back(a[i] + a[a.size()-1-j]);
        }
    }
    sort(possible_sums.begin(), possible_sums.end());
    possible_sums.resize(unique(possible_sums.begin(), possible_sums.end()) - possible_sums.begin());
    shuffle(possible_sums.begin(), possible_sums.end(), rng);
    for (int s: possible_sums){
        if (!solvable(n, s)) continue;
        vector<pair<int, int>> result = solve(s);
        if (result.size() != n/2) continue;
        for (int i=0; i<result.size(); i++){
            cout << result[i].first << " ";
        }
        for (int i=result.size()-1; i>=0; i--){
            cout << result[i].second << " \n"[!i];
        }
        break;
    }
}

Compilation message (stderr)

tabletennis.cpp: In function 'int main()':
tabletennis.cpp:48:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   48 |     for (int i=0; i<a.size(); i++) cin >> a[i];
      |                   ~^~~~~~~~~
tabletennis.cpp:62:27: warning: comparison of integer expressions of different signedness: 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   62 |         if (result.size() != n/2) continue;
      |             ~~~~~~~~~~~~~~^~~~~~
tabletennis.cpp:63:24: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   63 |         for (int i=0; i<result.size(); i++){
      |                       ~^~~~~~~~~~~~~~

• 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