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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. int main() {
  5.     ios::sync_with_stdio(false);
  6.     cin.tie(nullptr);
  7.  
  8.     int t;
  9.     cin >> t;
  10.     while (t--) {
  11.         int n, m;
  12.         cin >> n >> m;
  13.         vector<int> a(n);
  14.         for (int i = 0; i < n; i++) cin >> a[i];
  15.  
  16.         sort(a.begin(), a.end());
  17.  
  18.         int left = 0, right = n - 1;
  19.         int countPairs = 0;
  20.  
  21.         while (left < right) {
  22.             int sum = a[left] + a[right];
  23.             if (sum == m) {
  24.                 countPairs++;
  25.                 left++;
  26.                 right--;
  27.             } else if (sum < m) {
  28.                 left++;
  29.             } else {
  30.                 right--;
  31.             }
  32.         }
  33.  
  34.         cout << countPairs << "\n";
  35.     }
  36.     return 0;
  37. }
  38.  
Success #stdin #stdout 0.01s 5320KB
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https://ideone.com/CvmdV1
language:
C++ (gcc 8.3)
created:
3 hours ago
visibility:
public

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