'', 2 => '+', 3 => '-', 4 => '**' ); return $operator_map[$operator_number]; } $expression = ''; // For each permutation of operators, do... // (An operator can be a plus sign, minus sign, or empty string. // Which will result in expressions like: 1+2, 1-2 or 12) for ($a = 1; $a <= 4; $a++) { for ($b = 1; $b <= 4; $b++) { for ($c = 1; $c <= 4; $c++) { for ($d = 1; $d <= 4; $d++) { for ($e = 1; $e <= 4; $e++) { for ($f = 1; $f <= 4; $f++) { for ($g = 1; $g <= 4; $g++) { for ($h = 1; $h <= 4; $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 >= 1 && $result <= 100) { $result_array[$result] = $expression; } } } } } } } } } // Output the solutions (1 to 100). for ($i = 1; $i <= 100; $i++) { if (isset($result_array[$i])) { $expression = $result_array[$i]; echo "$i = $expression
"; } else { echo "$i = NO SOLUTION
"; } } ?>

Fun With Digits Variation (+ - **)