Given an alphanumeric string, find the number of times a pattern 1(0+)1 occurs in the given string. Here, (0+) signifies the presence of non empty sequence of consecutive 0’s.
Input : 1001010001 Output : 3 First sequence is in between 0th and 3rd index. Second sequence is in between 3rd and 5th index. Third sequence is in between 5th and 9th index. So total number of sequences comes out to be 3. Input : 1001ab010abc01001 Output : 2 First sequence is in between 0th and 3rd index. Second valid sequence is in between 13th and 16th index. So total number of sequences comes out to be 2.
The idea to solve this problem is to first find a ‘1’ and keep moving forward in the string and check as mentioned below:
- If any character other than ‘0’ and ‘1’ is obtained then it means pattern is not valid. So we go on in the search of next ‘1’ from this index and repeat these steps again.
- If a ‘1’ is seen, then check for the presence of ‘0’ at previous position to check the validity of sequence.
Below is the implementation of above idea:
Time Complexity: O( N ), where N is the length of input string.
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