Find Position of many elements in a large list.
- To: mathgroup at smc.vnet.net
- Subject: [mg127670] Find Position of many elements in a large list.
- From: benp84 at gmail.com
- Date: Tue, 14 Aug 2012 04:22:21 -0400 (EDT)
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I have a sorted, 1-dimensional list X of 1,000,000 integers, and a sorted, 1-dimensional list Y of 10,000 integers. Most, but not all, of the elements of Y are also elements of X. I'd like to know the positions of the elements in X that are also in Y. What's the fastest way to compute this?
I have an algorithm in mind but it requires lots of custom code and I'm wondering if there's a clever way to do it with built-in functions. Thanks.
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