Tetris-ing an array

Question

Consider the following array:

/www/htdocs/1/sites/lib/abcdedd
/www/htdocs/1/sites/conf/xyz
/www/htdocs/1/sites/conf/abc/         


        

Answer 1

Load them into a trie data structure. Starting from the parent node, see which is having a children count great than one. Once you find that magic node, just dismantle the parent node structure and have the current node as root.