Code for solving binary equations using regular expressions

Source: Internet
Author: User
Tags php example

Original article: http://blog.stevenlevithan.com/archives/algebra-with-regexes
I calculated the result based on the regular expression in the original text. Php example:

Copy codeThe Code is as follows: <? Php
/**
* Calculate Ax + By = C
*/
Function suan ($ A, $ B, $ C ){
$ --;
$ B --;
$ Str = str_repeat ('-', $ C );
$ Search = '/^ (. *) \ 1 {'. $ A. '} (. *) \ 2 {'. $ B. '} $ /';
Preg_match ($ search, $ str, $ r );
Return array ('x' => strlen ($ r [1]), 'y' => strlen ($ r [2]);
}
$ A = 2;
$ B = 3;
$ C = 9;
$ R = suan ($ A, $ B, $ C );
// Test
Echo 'calculate '. $ A. 'x +'. $ B. 'y = '. $ C.' <br/> ';
Echo 'X = '. ($ r [x]).' <br/> ';
Echo 'y = '. ($ r [y]);
// Output
// Calculate 2x + 3y = 9
// X = 3
// Y = 1
?>

I will explain
In a simple formula: 2x + 3y = 9

Principle:
This function generates such a regular expression.Copy codeThe Code is as follows: ^ (. *) \ 1 {1} (. *) \ 2 {2} $

To match a repeated string "-" with a length of 9, the length of the two groups is the value of x and y.

Regular Expression explanation:
[(. *)] Is a number ranging from 0 to countless.
\ 1 is to reference a group. The following [{1}] is repeated once.
The second half is \ 2, which is to reference two groups. The following [{2}] is repeated once.
The translation of the English blog is as follows:
The expression [^ (. *) \ 1 {16} (. *) \ 2 {11} $] of the binary equation 17x + 12y = 51 ]. It's easy to understand. [(. *)] Is a number ranging from 0 to countless. (This is followed by the above. In fact, [.] point number indicates the character "1 ")
That is, 0 to countless 1, followed by [\ 1] reference once. The next [{16}] is 16 times. Act on the previous [\ 1], that is, 16 references. In addition, the initial [(. *)] is exactly 17 times. The other one will not talk about it, just like this one.
The RegEx engine tries 【(. *): attempts to add 0 to countless characters including "1", 0 characters "1", 1 character "1", and 2 characters "1. Otherwise, the maximum number of all characters "1" (51 characters "1") must be tried ").

PS: when there is no solution, both x and y are 0.

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: info-contact@alibabacloud.com and provide relevant evidence. A staff member will contact you within 5 working days.

A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

  • Sales Support

    1 on 1 presale consultation

  • After-Sales Support

    24/7 Technical Support 6 Free Tickets per Quarter Faster Response

  • Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.