# Extract maximum numeric value from a given string | Set 2 (Regex approach)

• Difficulty Level : Easy
• Last Updated : 27 Dec, 2022

Given an alphanumeric string, extract maximum numeric value from that string. Examples:

```Input : 100klh564abc365bg
Output : 564
Maximum numeric value among 100, 564
and 365 is 564.
Input : abchsd0365sdhs
Output : 365```

In Set 1, we have discussed general approach for extract numeric value from given string.In this post, we will discuss regular expression approach for same. Below is one of the regular expression for at least one numeric digit.

`\d+`

So Regex solution is simple:

1. Initialize MAX = 0
2. Run loop over matcher, whenever match found, convert numeric string to integer and compare it with MAX.
• If number greater than MAX, update MAX to number.
3. Return MAX at the last.

Implementation:

## Java

 `// Java regex program to extract the maximum value` `import` `java.util.regex.Matcher;``import` `java.util.regex.Pattern;` `class` `GFG``{``    ``// Method to extract the maximum value``    ``static` `int` `extractMaximum(String str)``    ``{``        ``// regular expression for atleast one numeric digit``        ``String regex = ``"\\d+"``;``        ` `        ``// compiling regex``        ``Pattern p = Pattern.compile(regex);``        ` `        ``// Matcher object``        ``Matcher m = p.matcher(str);``        ` `        ``// initialize MAX = 0``        ``int` `MAX = ``0``;``        ` `        ``// loop over matcher``        ``while``(m.find())``        ``{``            ``// convert numeric string to integer``            ``int` `num = Integer.parseInt(m.group());``            ` `            ``// compare num with MAX, update MAX if num > MAX``            ``if``(num > MAX)``                ``MAX = num;``        ``}``        ` `        ``return` `MAX;``    ``}` `    ``public` `static` `void` `main (String[] args)``    ``{``        ``String str = ``"100klh564abc365bg"``;``        ` `        ``System.out.println(extractMaximum(str));``    ``}``}`

## C#

 `// C# regex program to extract the maximum value``using` `System;``using` `System.Text.RegularExpressions;` `class` `GFG``{``  ``// Method to extract the maximum value``  ``static` `int` `extractMaximum(``string` `str)``  ``{` `    ``// Regex object``    ``Regex regex = ``new` `Regex(``@"\d+"``);`  `    ``// initialize MAX = 0``    ``int` `MAX = 0;` `    ``// loop over matcher``    ``foreach` `(Match ItemMatch ``in` `regex.Matches(str))``    ``{``      ``// convert numeric string to integer``      ``int` `num = Int32.Parse(ItemMatch.Value);` `      ``// compare num with MAX, update MAX if num > MAX``      ``if``(num > MAX)``        ``MAX = num;``    ``}` `    ``return` `MAX;   ``  ``}` `  ``static` `public` `void` `Main ()``  ``{``    ``string` `str = ``"100klh564abc365bg"``; ``    ``Console.WriteLine(extractMaximum(str));``  ``}``}` `// This code is contributed by kothavvsaakash`

## Python3

 `# Python regex program to extract the maximum value``import` `re` `# Method to extract the maximum value``def` `extractMaximum(``str``):``  ` `    ``# regular expression for atleast one numeric digit``    ``regex ``=` `"\\d+"``    ` `    ``# compiling regex``    ``p ``=` `re.``compile``(regex)``    ` `    ``# initialize MAX = 0``    ``MAX` `=` `0``    ` `    ``# loop over matcher``    ``for` `m ``in` `re.finditer(p,``str``):``      ` `        ``# convert numeric string to integer``        ``num``=``int``(m.group(``0``))``        ` `        ``# compare num with MAX, update MAX if num > MAX``        ``if``(num > ``MAX``):``            ``MAX` `=` `num``            ` `    ``return` `MAX``    ` `str``=``"100klh564abc365bg"``print``(extractMaximum(``str``))` `# This code is contributed by Pushpesh Raj.`

Output

`564`

Time complexity : O(n)
Auxiliary Space : O(1)

But above program wouldn’t work if number is greater that integer range. You can try parseLong() method for numbers upto long range.But to handle the case of large numbers(greater than long range) we can take help of BigInteger class in java. Below is the java program to demonstrate the same.

Implementation:

## Java

 `// Java regex program to extract the maximum value``// in case of large numbers` `import` `java.math.BigInteger;``import` `java.util.regex.Matcher;``import` `java.util.regex.Pattern;` `class` `GFG``{``    ``// Method to extract the maximum value``    ``static` `BigInteger extractMaximum(String str)``    ``{``        ``// regular expression for atleast one numeric digit``        ``String regex = ``"\\d+"``;``        ` `        ``// compiling regex``        ``Pattern p = Pattern.compile(regex);``        ` `        ``// Matcher object``        ``Matcher m = p.matcher(str);``        ` `        ``// initialize MAX = 0``        ``BigInteger MAX = BigInteger.ZERO;``        ` `        ``// loop over matcher``        ``while``(m.find())``        ``{``            ``// convert numeric string to BigInteger``            ``BigInteger num = ``new` `BigInteger(m.group());``            ` `            ``// compare num with MAX, update MAX if num > MAX``            ``if``(num.compareTo(MAX) > ``0``)``                ``MAX = num;``        ``}``        ` `        ``return` `MAX;``    ``}` `    ``public` `static` `void` `main (String[] args)``    ``{``        ``String str = ``"100klh564231315151313151315abc365bg"``;``        ` `        ``System.out.println(extractMaximum(str));``    ``}``}`

Output

`564231315151313151315`

Time complexity : O(n)
Auxiliary Space : O(1)

This article is contributed by Gaurav Miglani. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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