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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. #define ll long long
  4. // #define int long long int
  5. #define ld long double
  6. #define all(x) x.begin(), x.end()
  7. #define sortall(x) sort(all(x))
  8. #define endl '\n'
  9. #define fast ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
  10. template<class T>
  11. void printC (T Collection)
  12. {
  13.     for (auto&i:Collection)
  14.         cout << i << " \n";
  15.     cout << '\n';
  16. }
  17.  
  18. /*
  19.  * Think twice, code once
  20.  * Think of different approaches to tackle a problem: write them down.
  21.  * Think of different views of the problem. don't look from only one side.
  22.  * don't get stuck in one approach.
  23.  * common mistakes: - over_flow
  24.  *                  - out_of_bound index
  25.  *                  - infinite loop
  26.  *                  - corner cases
  27.  *                  - duplication counting.
  28. */
  29.  
  30. void solve()
  31. {
  32.     int n, x; cin >> n >> x;
  33.     vector<int> v(n);
  34.     unordered_map<int, pair<int, int>> pos;
  35.     for (int i = 0; i < v.size(); ++i)
  36.     {
  37.         cin >> v[i];
  38.         if (pos[v[i]].first == 0)
  39.             pos[v[i]].first = i+1;
  40.         else
  41.             pos[v[i]].second = i+1;
  42.     }
  43.     sort(all(v));
  44.     int l = 0, r = v.size()-1;
  45.     while (l < r)
  46.     {
  47.         if (v[l] + v[r] == x)
  48.         {
  49.             if (pos[v[l]].first != pos[v[r]].first)
  50.                 cout << pos[v[l]].first << ' ' << pos[v[r]].first;
  51.             else
  52.                 cout << pos[v[l]].first << ' ' << pos[v[r]].second;
  53.             return;
  54.         }else if (v[l] + v[r] < x)
  55.             l++;
  56.         else
  57.             r--;
  58.     }
  59.     cout << "IMPOSSIBLE";
  60. }
  61.  
  62. int32_t main()
  63. {
  64.     // #ifndef ONLINE_JUDGE
  65.     //     freopen("input.txt", "r", stdin);
  66.     //     freopen("output.txt", "w", stdout);
  67.     //     freopen("Errors.txt", "w", stderr);
  68.     // #endif
  69.     fast
  70.     int t = 1;
  71.     // cin >> t;
  72.     while (t--)
  73.     {
  74.         solve();
  75.         if (t) cout << '\n';
  76.     }
  77.     cout << '\n';
  78.     return 0;
  79. }
Success #stdin #stdout 0.01s 5288KB
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Standard input is empty
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IMPOSSIBLE
https://ideone.com/xgwf94
language:
C++14 (gcc 8.3)
created:
8 days ago
visibility:
public

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