'', 2 => '+', 3 => '-'/*, 4 => '*', 5 => '/'*/ ); // Get an operator, (or empty string), // give a number. function get_operator($operator_number) { $operator_map = $GLOBALS['operator_map']; return $operator_map[$operator_number]; } $expression = ''; $number_of_operators = count($operator_map); $result_array = array(); // For each permutation of operators, do... // (An operator can be a plus sign, minus sign, or empty string. // Which will result in expressions like: 1+2, 1-2 or 12) for ($a = 1; $a <= $number_of_operators; $a++) { for ($b = 1; $b <= $number_of_operators; $b++) { for ($c = 1; $c <= $number_of_operators; $c++) { for ($d = 1; $d <= $number_of_operators; $d++) { for ($e = 1; $e <= $number_of_operators; $e++) { for ($f = 1; $f <= $number_of_operators; $f++) { for ($g = 1; $g <= $number_of_operators; $g++) { for ($h = 1; $h <= $number_of_operators; $h++) { // Create an expression like: // 1-2+34+5-6-7-8-9 $expression = '1' . get_operator($a) . '2' . get_operator($b) . '3' . get_operator($c) . '4' . get_operator($d) . '5' . get_operator($e) . '6' . get_operator($f) . '7' . get_operator($g) . '8' . get_operator($h) . '9'; // Evaluate the expression, // e.g. "1-2+34+5-6-7-8-9" evaluates // to 8. $result = eval("return $expression;"); if (is_int($result) && $result == 100) { $result_array[] = $expression; } } } } } } } } } // Output the solutions. foreach ($result_array as $expression) { echo "100 = $expression
"; } ?>

Fun With Digits (Original)