Find all the patterns of "1(0+)1" in a given string using Regular Expression

In Set 1, we have discussed general approach for counting the patterns of the form 1(0+)1 where (0+) represents any non-empty consecutive sequence of 0’s.In this post, we will discuss regular expression approach to count the same. Examples:

Input : 1101001
Output : 2

Input : 100001abc101
Output : 2

Below is one of the regular expression for above pattern

10+1

Hence, whenever we found a match, we increase counter for counting the pattern.As last character of a match will always '1', we have to again start searching from that index. 

Implementation:

2

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

Related Articles :

• Regular Expression Java
• Quantifiers
• Extracting each word from a String using Regex
• Check if a given string is a valid number (Integer or Floating Point)
• Print first letter of each word in a string using regex