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The next in the series of 'big arithmetic' multiplies together two very large positive integer numbers.
Note that 'big_multiply' uses the other big arithemetic function ,'big_addition', to work, and must be incuded with the function.
| <?php
$number_one = "106674437659978524323534368687676867987987976875764";
$number_two = "1258665764565487687698798744354358677768754234566789765443658798654243587940";
$answer = big_multiply ($number_one, $number_two);
print $answer;
function big_multiply ($number_one, $number_two) {
$length_one = strlen($number_one);
$length_two = strlen($number_two);
$row = "";
$digit_string = "";
$answer = "";
$zero_number = 0;
$carry = 0;
for ( $index_two = ($length_two - 1); $index_two >= 0; $index_two-- ) {
$zero_string = "";
for ( $index = 1; $index <= $zero_number; $index++ ) {
$zero_string = $zero_string . "0";
}
for ( $index_one = ($length_one - 1); $index_one >= 0; $index_one-- ) {
$digit = ((( integer ) $number_two[$index_two]) * (( integer ) $number_one[$index_one])) + $carry;
$digit_string = ( string ) $digit;
if ($digit >= 10) {
$row = $row . $digit_string[1];
$carry = ( integer ) $digit_string[0];
}
else {
$row = $row . $digit_string;
$carry = 0;
}
}
if ($carry != 0) {
$row = $row . ( string ) $carry;
}
$row = $zero_string . $row;
$row = strrev($row);
$answer = big_addition ($answer, $row);
$row = "";
$carry = 0;
$zero_number++;
}
$flag = 0;
$length = strlen($answer);
for ( $index = 0; $index <= ($length - 1); $index++ ) {
if ($answer[$index] != "0") {
$flag = 1;
}
}
if ($flag == 0) {
$answer = "0";
}
return $answer;
}
function big_addition ($number_one, $number_two) {
if (strlen($number_one) > strlen($number_two)) {
$longer_length = strlen($number_one);
$shorter_length = strlen($number_two);
$set_one = $number_one;
$zero_number = ($longer_length - $shorter_length);
$zero_string = "";
for ( $index = 1; $index <= $zero_number; $index++ ) {
$zero_string = $zero_string . "0";
}
$set_two = $zero_string . $number_two;
$length = strlen($number_one);
}
if (strlen($number_one) < strlen($number_two)) {
$longer_length = strlen($number_two);
$shorter_length = strlen($number_one);
$set_two = $number_two;
$zero_number = ($longer_length - $shorter_length);
$zero_string = "";
for ( $index = 1; $index <= $zero_number; $index++ ) {
$zero_string = $zero_string . "0";
}
$set_one = $zero_string . $number_one;
$length = strlen($number_two);
}
if (strlen($number_one) == strlen($number_two)) {
$set_one = $number_one;
$set_two = $number_two;
$length = strlen($number_one);
}
$carry = 0;
$answer = "";
for ( $index = ($length - 1); $index >= 0; $index-- ) {
$digit = $carry + (( integer ) $set_one[$index]) + (( integer ) $set_two[$index]);
$digit_string = (( string ) $digit);
if ($digit >= 10) {
$answer = $answer . $digit_string[1];
$carry = ( integer ) $digit_string[0];
}
else {
$answer = $answer . $digit_string;
$carry = 0;
}
}
if ($carry != 0) {
$carry_string = (( string ) $carry);
$answer = $answer . $carry_string;
}
$answer = strrev($answer);
return $answer;
}
?> | |
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| | | | P C wrote : 1090
I tried out the script without changing an iota, and it worked perfectly, meaning that I transcribed the result to my desk calculator (dc) and repeated the calculations there, subtracted the two results, and I got a difference of zero.
Good script, Jeremy!
| | | | jeremy watts wrote : 1091
thanks for the comment cp. glad it worked for you! not sure of its limits yet, but they`re pretty big as some of the numbers i`ve entered have been huge. anyway who gave me the low score and why?????
| | | | P C wrote :1092
If they give a low grade without giving a reason, it could be that grade was not for the programming aspects, but more to the usefulness or practicality of the code.
I do understand why not many people are not interested in this highly mathematical challenge. Those who have tried calculating pi to 20,000 digits, or tried to factorize a big number will understand.
Do not get discouraged by a few negative comments, keep up the good work.
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