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  1. #include<bits/stdc++.h>
  2. #define f1(i, n) for(int i=1;i<=n;++i)
  3. #define f0(i, n) for(int i=0;i<n;++i)
  4. #define ull unsigned long long
  5. #define ll long long
  6. #define rev(a) reverse(a.begin(),a.end())
  7. #define all(x) x.begin(),x.end()
  8. #define so(A, n) sort(A+1, A+n+1)
  9. using namespace std;
  10. const int maxn = 1e6 + 1;
  11. const int N = 2e5 + 1;
  12. const ll MOD = 1e9 + 7;
  13. ll A[N], pre[N];
  14. string multiply(string num1, string num2) {
  15.     int len1 = num1.size();
  16.     int len2 = num2.size();
  17.     vector<int> result(len1 + len2, 0);
  18.  
  19.     // Nhân từng chữ số
  20.     for (int i = len1 - 1; i >= 0; i--) {
  21.         for (int j = len2 - 1; j >= 0; j--) {
  22.             int mul = (num1[i] - '0') * (num2[j] - '0');
  23.             int pos1 = i + j;
  24.             int pos2 = i + j + 1;
  25.             int sum = mul + result[pos2];
  26.  
  27.             result[pos2] = sum % 10;
  28.             result[pos1] += sum / 10;
  29.         }
  30.     }
  31.  
  32.     // Chuyển vector kết quả thành chuỗi
  33.     string product = "";
  34.     for (int digit : result) {
  35.         if (!(product.empty() && digit == 0)) {
  36.             product += to_string(digit);
  37.         }
  38.     }
  39.  
  40.     return product.empty() ? "0" : product;
  41. }
  42. int compareBigNumbers(string a, string b) {
  43.     // Bỏ số 0 ở đầu (nếu có)
  44.     a.erase(0, a.find_first_not_of('0'));
  45.     b.erase(0, b.find_first_not_of('0'));
  46.  
  47.     // So độ dài trước
  48.     if (a.length() > b.length()) return 1;
  49.     if (a.length() < b.length()) return -1;
  50.  
  51.     // Nếu độ dài bằng nhau thì so từng chữ số
  52.     for (size_t i = 0; i < a.length(); ++i) {
  53.         if (a[i] > b[i]) return 1;
  54.         if (a[i] < b[i]) return -1;
  55.     }
  56.  
  57.     return 0; // Hai số bằng nhau
  58. }
  59. int main() {
  60.     ios_base::sync_with_stdio(0);
  61.     cin.tie(0);
  62.     cout.tie(0);
  63.     int n;
  64.     cin >> n;
  65.     f1(i, n) {
  66.         cin >> A[i];
  67.         pre[i] = pre[i - 1] + A[i];
  68.     }
  69.     ll pos = 1;
  70.     string max_sum = "0";
  71.     for (ll i = 1; i < n; ++i) {
  72.         string motcaigiday = multiply(to_string(pre[i]), to_string((pre[n] - pre[i])));
  73.         int comp = compareBigNumbers(motcaigiday, max_sum);
  74.         if (comp == 1) {
  75.             max_sum = motcaigiday;
  76.             pos = i;
  77.         }
  78.     }
  79.     cout << pos;
  80.  
  81.  
  82. }
  83.  
Success #stdin #stdout 0.01s 5288KB
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https://ideone.com/MqAQ2e
language:
C++14 (gcc 8.3)
created:
7 days ago
visibility:
public

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