RE: Pattern Matching in Lists

• To: mathgroup at smc.vnet.net
• Subject: [mg35569] RE: [mg35547] Pattern Matching in Lists
• From: "DrBob" <majort at cox-internet.com>
• Date: Fri, 19 Jul 2002 06:08:38 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

```How's this?

w = {1, 1, 1, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0};
Count[Transpose[{Drop[w, -1], Drop[w, 1]}], {1, 0}]

4

If you want the list treated as a cycle, so that 1 at the end and 0 at
the beginning counts as a match, here's a different example input and
different counting method:

w2 = {0, 1, 1, 1, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 1};
Count[Transpose[{w2, RotateRight[w2, 1]}], {1, 0}]

5

Bobby Treat

-----Original Message-----
From: Anthony Mendes [mailto:amendes at zeno.ucsd.edu]
To: mathgroup at smc.vnet.net
Subject: [mg35569] [mg35547] Pattern Matching in Lists

Hello,

Suppose w={1,1,1,0,0,1,0,1,0,0,1,0,0}.

How can I count the number of occurrences of a 1 in w immediately
followed by a 0 in w?

I have tried every incarnation of Count[] I can think of; for example,

Count[w,{___,1,0,___}]

does not seem to work.  In general, how can I count the number of
occurrences of a 1 followed by a 0 in a list of 1's and 0's?  Thank you!

--
Tony
_____________________
amendes at math.ucsd.edu

```

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