Re: Number of duplicates in an array?

2008/8/18 tedd <tedd@sperling.com>: > Anyone have a cool method of finding duplicate items in an array and the > number of times they appear? > > I'm doing it in a way that is probably less than optimum. I want to see how > you guys solve it. Hmm. Assuming the following inputs and outputs: $input_array = array( 'one', 'two', 'three', 'one', 'two', 'one' ); $output_array = array( 'one' => 3, 'two' => 2, 'three' => 1 ); $input_array = array( 'one', 'two', 'three', 'one', 'two', 'one' ); $output_array = array(); foreach( $input_array as $input ) { if ( !isset( $output_array[$input] ) ) { $output_array[$input] = 0; } $output_array[$input]++; } Untested code. From a CompSci PoV, input_array is a list while output_array would be better implemented as a binary tree (with the normal caveats about tree balancing). But given that we're working in PHP and your data sets probably aren't that large, this is the "good enough" solution. -- http://www.otton.org/