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  1. #include <iostream>
  2. #include <vector>
  3.  
  4. int main() {
  5. 	auto m = 2; // #rows
  6. 	auto n = 3; // #cols
  7. 	// row-major vector
  8. 	auto x = std::vector<double>{1,2,3,4,5,6};
  9.  
  10. 	auto const colIndex = 1;
  11. 	auto const col = std::vector<double>{7,8};
  12. 	// insert column {7,8} into the 2nd position
  13. 	// =>{1,7,2,3,4,8,5,6}
  14.  
  15.     {
  16.         x.resize(x.size() + col.size());
  17.  
  18.         // we'll start shifting elements over from the right
  19.         double *from = &x[m * n];
  20.         const double *src = &col[m];
  21.         double *to = from + m;
  22.  
  23.         size_t R = n - colIndex; // number of cols left of the insert
  24.         size_t L = colIndex;     // number of cols right of the insert
  25.  
  26.         while (to != &x[0]) {
  27.             for (size_t i = 0; i < R; ++i) *(--to) = *(--from);
  28.             *(--to) = *(--src); // insert value from new column
  29.             for (size_t i = 0; i < L; ++i) *(--to) = *(--from);
  30.         }
  31.     };
  32.  
  33. 	for(auto const& xi : x)
  34. 		std::wcout << xi << L" ";
  35.  
  36. 	return 0;
  37. }
Success #stdin #stdout 0s 4348KB
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stdin 
Standard input is empty
stdout 
1 7 2 3 4 8 5 6
https://ideone.com/z2MwbM
language:
C++14 (gcc 8.3)
created:
6 years ago
visibility:
public

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