NFA (Algorithms 4/e)

Object
- edu.princeton.cs.algs4.NFA

```
public class NFA
extends Object
```
The NFA class provides a data type for creating a nondeterministic finite state automaton (NFA) from a regular expression and testing whether a given string is matched by that regular expression. It supports the following operations: concatenation, closure, binary or, and parentheses. It does not support mutiway or, character classes, metacharacters (either in the text or pattern), capturing capabilities, greedy or reluctant modifiers, and other features in industrial-strength implementations such as Pattern and Matcher.
This implementation builds the NFA using a digraph and a stack and simulates the NFA using digraph search (see the textbook for details). The constructor takes time proportional to m, where m is the number of characters in the regular expression. The recognizes method takes time proportional to m n, where n is the number of characters in the text.
For additional documentation, see Section 5.4 of Algorithms, 4th Edition by Robert Sedgewick and Kevin Wayne.

Author:

Robert Sedgewick, Kevin Wayne

Constructor Summary

Constructors
Constructor Description

NFA(String regexp)
Initializes the NFA from the specified regular expression.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`static void`	`main(String[] args)`	Unit tests the `NFA` data type.
`boolean`	`recognizes(String txt)`	Returns true if the text is matched by the regular expression.

Methods inherited from class java.lang.Object
clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - NFA
```
public NFA(String regexp)
```
    Initializes the NFA from the specified regular expression.
    
    Parameters:
    
    regexp - the regular expression
- Method Detail
  - recognizes
```
public boolean recognizes(String txt)
```
    Returns true if the text is matched by the regular expression.
    
    Parameters:
    
    txt - the text
    
    Returns:
    
    true if the text is matched by the regular expression, false otherwise
  - main
```
public static void main(String[] args)
```
    Unit tests the NFA data type.
    
    Parameters:
    
    args - the command-line arguments