Regular Expression Matching in String
Given a text and a pattern, evaluate the pattern to see if it matches the text by using regular expression matching.
Statement
Given a text and a pattern, determine if the pattern matches the text completely or not at all by using regular expression matching. For simplicity, assume that the pattern may contain only two operators: . and *.
* operator in the pattern means that the character preceding * may not appear or may appear any number of times in the text. The . operator matches with any character in the text exactly once.
Example
Below is an example of a text and its matching and non-matching patterns:
Sample input
Text = fabbbc
Pattern = .ab*c
Expected output
true
Try it yourself #
#include <iostream>#include <string>using namespace std;bool RegxMatch(const string& text, const string& pattern) {//TODO: Write - Your - Codereturn false;}
Solution 1
If there are no operators in the pattern, then regex matching is a simple string comparison. Handling the . operator is also very easy as it can match with any character in the text. However, handling the * operator is not that simple. To handle *, let’s look at the below example.
Suppose the given text is fabbbc, and the given pattern is .ab*c. We start matching from the first character of both the text and the pattern. The first character of the pattern is . and the first character of the text is f. Since . matches with any character, they match. Now, we match the remaining text and the remaining pattern recursively , that is, we match ab*c and abbbc.
For the remaining text ...