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  1. #include <iostream>
  2. #include <vector>
  3. #include <cassert>
  4.  
  5. void permute_impl(size_t width, std::vector<std::vector<int>> const &mat,
  6.                   size_t column, std::vector<int> &prefix) {
  7.   if (column < width) {
  8.     for (auto &row : mat) {
  9.       prefix.push_back(row[column]);
  10.       permute_impl(width, mat, column + 1, prefix);
  11.       prefix.pop_back();
  12.     }
  13.   } else {
  14.     for (auto i : prefix)
  15.       std::cout << i << ' ';
  16.     std::cout << '\n';
  17.   }
  18. }
  19.  
  20. void permute(std::vector<std::vector<int>> const &mat) {
  21.   if (mat.empty())
  22.     return;
  23.   std::vector<int> prefix;
  24.   size_t N = mat[0].size();
  25.   // assert that all rows are the same size
  26.   for (auto &row : mat)
  27.     assert(row.size() == N);
  28.   permute_impl(N, mat, 0, prefix);
  29. }
  30.  
  31. int main() {
  32.   std::vector<std::vector<int>> mat = {
  33.       {0, 1, 2}, {3, 4, 5}, {6, 7, 8},
  34.   };
  35.  
  36.   permute(mat);
  37. }
Success #stdin #stdout 0s 3416KB
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stdin
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Standard input is empty
stdout
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0 1 2 
0 1 5 
0 1 8 
0 4 2 
0 4 5 
0 4 8 
0 7 2 
0 7 5 
0 7 8 
3 1 2 
3 1 5 
3 1 8 
3 4 2 
3 4 5 
3 4 8 
3 7 2 
3 7 5 
3 7 8 
6 1 2 
6 1 5 
6 1 8 
6 4 2 
6 4 5 
6 4 8 
6 7 2 
6 7 5 
6 7 8
https://ideone.com/bfTBGa
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
public

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