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/* ************************************************************** * C++ Mathematical Expression Toolkit Library * * * * ExprTk N-Queens Problem * * Author: Arash Partow (1999-2024) * * URL: https://www.partow.net/programming/exprtk/index.html * * * * Copyright notice: * * Free use of the Mathematical Expression Toolkit Library is * * permitted under the guidelines and in accordance with the * * most current version of the MIT License. * * https://www.opensource.org/licenses/MIT * * SPDX-License-Identifier: MIT * * * ************************************************************** */ #include #include "exprtk.hpp" template void sudoku_solver() { typedef exprtk::symbol_table symbol_table_t; typedef exprtk::expression expression_t; typedef exprtk::parser parser_t; typedef exprtk::function_compositor compositor_t; typedef typename compositor_t::function function_t; const T n = T(15); std::vector board(static_cast(n), T(- 1)); exprtk::rtl::io::package io_package; symbol_table_t symbol_table; symbol_table.add_constant("n" , n ); symbol_table.add_vector ("board" , board); symbol_table.add_package (io_package); compositor_t compositor(symbol_table); compositor.load_variables(true); compositor.load_vectors (true); compositor.add( function_t("display_board") .expression ( " for (var row := 0; row < n; row += 1) " " { " " for (var col := 0; col < n; col += 1) " " { " " print((board[row] == col) ? ' Q ' : ' . '); " " }; " " " " println(''); " " } " )); compositor.add( function_t("is_valid") .vars("row", "col") .expression ( " for (var i := 0; i < row; i += 1) " " { " " if ( " " (board[i] == col) or " " (abs(board[i] - col) == abs(i - row)) " " ) " " { " " return [false]; " " } " " }; " " " " return [true]; " )); compositor.add( function_t("solve_nqueens") .var("row") .expression ( " if (row == n) " " { " " return [true]; " " }; " " " " for (var col := 0; col < n; col += 1) " " { " " if (is_valid(row, col)) " " { " " board[row] := col; " " " " if (solve_nqueens(row + 1)) " " { " " return [true]; " " } " " } " " }; " " " " return [false]; " )); const std::string sudoku_solver_program = " if (solve_nqueens(0)) " " { " " println('N-Queens Puzzle Solved!'); " " } " " else " " { " " println('Error: Failed to solve n-queens puzzle.'); " " }; " " " " display_board(); "; expression_t expression; expression.register_symbol_table(symbol_table); parser_t parser; parser.compile(sudoku_solver_program,expression); expression.value(); } int main() { sudoku_solver(); return 0; }