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| 1 | +class Solution { |
| 2 | + |
| 3 | + /** |
| 4 | + * @param String $num1 |
| 5 | + * @param String $num2 |
| 6 | + * @return String |
| 7 | + */ |
| 8 | + function multiply($num1, $num2) { |
| 9 | + if ($num1 == "0" || $num2 == "0") return "0"; |
| 10 | + $res = array_fill(0, strlen($num1) + strlen($num2), 0); |
| 11 | + $a = 0; |
| 12 | + for ($i = strlen($num2) - 1; $i >= 0; $i--) { |
| 13 | + $b = 0; |
| 14 | + for ($j = strlen($num1) - 1; $j >= 0; $j--) { |
| 15 | + $prod = (ord($num1[$j]) - ord('0')) * (ord($num2[$i]) - ord('0')); |
| 16 | + $prod += $res[$a+$b]; |
| 17 | + $carry = intval($prod/10); |
| 18 | + $digit = $prod%10; |
| 19 | + $res[$a+$b] = $digit; |
| 20 | + $res[$a+$b+1] += $carry; |
| 21 | + $b++; |
| 22 | + } |
| 23 | + $a++; |
| 24 | + } |
| 25 | + $sb = ""; |
| 26 | + for ($i = count($res) - 1; $i >= 0; $i--) { |
| 27 | + if ($i == count($res) -1 && $res[count($res) - 1] == 0) continue; |
| 28 | + $sb .= chr($res[$i] + ord('0')); |
| 29 | + } |
| 30 | + return $sb; |
| 31 | + } |
| 32 | +} |
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