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  1. #include <iostream>
  2. #include <vector>
  3. using namespace std;
  4.  
  5. int main() {
  6.     vector<vector<int>> nums = {
  7.         {1,4,6,3,8,2},
  8.         {3,5,1,9,7,4},
  9.         {5,2,7,5,9,1}
  10.     };
  11.  
  12.     int l = 2, r = 4;   // Sum from index 2 to 4 (inclusive)
  13.  
  14.     // Prefix sum for each row
  15.     vector<vector<int>> prefix(nums.size());
  16.  
  17.     for (int i = 0; i < nums.size(); i++) {
  18.         prefix[i].resize(nums[i].size());
  19.  
  20.         prefix[i][0] = nums[i][0];
  21.  
  22.         for (int j = 1; j < nums[i].size(); j++) {
  23.             prefix[i][j] = prefix[i][j - 1] + nums[i][j];
  24.         }
  25.     }
  26.  
  27.     // Answer queries
  28.     for (int i = 0; i < nums.size(); i++) {
  29.         int sum;
  30.         if (l == 0)
  31.             sum = prefix[i][r];
  32.         else
  33.             sum = prefix[i][r] - prefix[i][l - 1];
  34.  
  35.         cout << "Sum: " << sum << endl;
  36.     }
  37.  
  38.     return 0;
  39. }
Success #stdin #stdout 0.01s 5288KB
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stdin
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Standard input is empty
stdout
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Sum: 17
Sum: 17
Sum: 21
https://ideone.com/cnpYex
language:
C++14 (gcc 8.3)
created:
1 day ago
visibility:
public

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