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  1. #include <bits/stdc++.h>
  2. #define VuDucNam ios_base::sync_with_stdio(false);
  3. #define Lop9a6 cin.tie(NULL);
  4. #define THCSPhamVanDong cout.tie(NULL);
  5. #define ll long long
  6. #define el cout << '\n'
  7. #define sz(a) (ll) a.size()
  8. #define all(a) a.begin(), a.end()
  9. #define fi first
  10. #define se second
  11. #define fill(a, x) memset(a, x, sizeof(a))
  12. #define file(name)                         \
  13.     if (fopen(name ".INP", "r"))           \
  14.     {                                      \
  15.         freopen(name ".INP", "r", stdin);  \
  16.         freopen(name ".OUT", "w", stdout); \
  17.     }
  18. #define TIME (1.0 * clock() / CLOCKS_PER_SEC)
  19. #define RUNTIME cerr << "\nRuntime: " << TIME << "s.\n"
  20.  
  21. using namespace std;
  22.  
  23. const ll MOD = 1e9 + 7;
  24. const ll inf = LLONG_MAX;
  25.  
  26. int n;
  27. ll k, ans = 0;
  28. vector<ll> a;
  29. unordered_map<ll, int> mp;
  30.  
  31. void solve()
  32. {
  33.     cin >> n;
  34.     cin.ignore();
  35.     string s;
  36.     getline(cin, s);
  37.     cin >> k;
  38.     string tmp = "";
  39.     for (int i = 0; i < sz(s); ++i){
  40.         char c = s[i];
  41.         if (isdigit(c) || c == '-'){
  42.             if (c == '-' && tmp.empty()){
  43.                 if (i + 1 < sz(s) && isdigit(s[i + 1]))
  44.                     tmp.push_back(c);
  45.                 else{
  46.                     if (!tmp.empty()){
  47.                         a.push_back(stoll(tmp));
  48.                         tmp = "";
  49.                     }
  50.                 }
  51.             }
  52.             else{
  53.                 tmp.push_back(c);
  54.             }
  55.         }else{
  56.             if (!tmp.empty()){
  57.                 a.push_back(stoll(tmp));
  58.                 tmp = "";
  59.             }
  60.         }
  61.     }
  62.     if (!tmp.empty()){
  63.         a.push_back(stoll(tmp));
  64.     }
  65.     for (int i = 0; i < sz(a); ++i){
  66.         ans += mp[k - a[i]];
  67.         mp[a[i]]++;
  68.     }
  69.     cout << ans;
  70.     el;
  71. }
  72.  
  73. int main()
  74. {
  75.     VuDucNam Lop9a6 THCSPhamVanDong
  76.     file("NHATKY");
  77.     solve();
  78.     RUNTIME;
  79.     return 0;
  80. }
  81.  
Success #stdin #stdout #stderr 0.01s 5292KB
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stdout
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Runtime: 0.004966s.
https://ideone.com/sM3wWp
language:
C++ (gcc 8.3)
created:
5 days ago
visibility:
public

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