RE: Pattern Matching in Lists

• To: mathgroup at smc.vnet.net
• Subject: [mg35563] RE: [mg35547] Pattern Matching in Lists
• From: "David Park" <djmp at earthlink.net>
• Date: Fri, 19 Jul 2002 06:08:18 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

```Anthony,

Here are three ways.

w = {1, 1, 1, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0};

w2 = Partition[w, 2, 1];
Count[w2, {1, 0}]
4

count = 0;
Do[If[w[[i]] == 1 && w[[i + 1]] == 0, count++],
{i, 1, Length[w] - 1}];
count
4

Count[Drop[w - RotateLeft[w], -1], 1]
4

David Park

From: Anthony Mendes [mailto:amendes at zeno.ucsd.edu]
To: mathgroup at smc.vnet.net

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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