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MathGroup Archive 2002

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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
djmp at earthlink.net
http://home.earthlink.net/~djmp/ 

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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