I have a string like"1 0 -1 2 0 1 0" . How to count the number of patterns that starts with 0 and ends with 0.

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Like in the above ex, there are two patterns(0 -1 2 0 and 0 1 0).
What will be the syntax for finding that out using regex in python?

What I have tried:

I've tried 'r^[0\s]-\d[1-9]' but it's not working!

Posted 18-Jul-20 1:45am

pavin mishra

Updated 18-Jul-20 2:03am

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BillWoodruff 18-Jul-20 19:43pm

are you familiar enough with C# to convert an example to Python ?

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OriginalGriff · Accepted Answer · 2020-07-18T02:03:00

Solution 1

A Regex isn't about "counting" - it's a text processing system.
But ... if you locate all the "<whitespace>0<whitespace>" entires as separate groups, you could tell haw many patterns there are that match your criteria - and a Regex will tell you the number of matches.
So in your sample "1 0 -1 2 0 1 0" there are three "<whitespace>0<whitespace>" entries, so depending on how you want to process them there are two or three different "patterns": 0 -1 2 0, 0 -1 2 0 1 0, and 0 1 0

Knowing the number of zeros, tells you the patterns count.

Posted 18-Jul-20 2:03am

OriginalGriff

Comments

BillWoodruff 18-Jul-20 19:48pm

not sure, in this case, if the OP needs some kind of backtracking that would return 0 -1 2 0 1 0 ... given the two results the OP describes.

OriginalGriff 19-Jul-20 2:19am

Why? If all you want is the number of simple patterns - and his sample implies that - the number of zeros tells you that - it's the number of gaps between zeros.
Or am I missing something?

BillWoodruff 19-Jul-20 3:58am

Hi, As I see it the OP wants '0' delimited patterns, like: '0 -1 2 0'

Consider: 0 0 1 2 3

Two zeroes, one pattern: '0 0' ... unless the OP tells us more explicitly how he wants to scan, there's uncertainty about ...