mysudokugenerator.exe

 #include <iostream>
 #include <array>
 #include <algorithm>
 #include <random>
 #include <bitset>

 typedef unsigned int uint;

 class Sudoku
 {
 public:
     Sudoku() noexcept
     :   gen(rd())
     {
         square.fill(0);
         std::generate(  std::begin(square),
                         std::end(square),
                         [](){ static uint i = 0; return ++i; });
         generate();
     }
     void print() noexcept
     {
         for (int i = 0; i < 81; ++i)
         {
             if (!(i%9) && i)
                 std::cout << "|\n";
             if (!(i%27))
                 std::cout << "+---+---+---+\n";
             if (!(i%3))
                 std::cout << "|";
             std::cout << board[i];
         }
         std::cout << "|\n+---+---+---+\n";
         std::cout << std::flush;
     }
     void generate() noexcept
     {
         // Use rejection sampling
         do
         {
             fillBoardSquare(0);     fillBoardSquare(3);     fillBoardSquare(6);
             fillBoardSquare(27);    fillBoardSquare(30);    fillBoardSquare(33);
             fillBoardSquare(54);    fillBoardSquare(57);    fillBoardSquare(60);
         } while (!validate());
     }

 private:
     std::array<uint,81> board;
     std::array<uint,9> square;
     std::random_device rd;
     std::mt19937 gen;

     void fillBoardSquare(size_t anchor) noexcept
     {
         std::shuffle(std::begin(square),std::end(square),gen);
         for (size_t i = 0; i < 9; ++i)
         {
             board[anchor+(i%3)] = square[i];
             if (i%3 == 2)
                 anchor += 9;
         }
     }
     bool validate() noexcept
     {
         bool valid = true;
         std::bitset<9> length;
         uint counter = 0;
         for (size_t i = 0; i < 9 && valid; ++i)
         {
             for (size_t j = 0; j < 9 && valid; ++j)
                 length.set(board[i + j*9]-1);
             if (valid = length.all())
                 length.reset();
             ++counter;
         }
         for (size_t j = 0; j < 9 && valid; ++j)
         {
             for (size_t i = 0; i < 9 && valid; ++i)
                 length.set(board[i + j*9]-1);
             if (valid = length.all())
                 length.reset();
             ++counter;
         }
         return valid;
     }
 };

 int main()
 {
     std::cout << "Here is your sudoku:\n";
     // You may be waiting a while
     Sudoku sudoku;
     sudoku.print();
     return 0;
 }