32-Section-Handout - CS106X Autumn 2010 Handout XX November...

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CS106X Handout XX Autumn 2010 November 17 th , 2010 Section Handout Problem 1: Dictionaries and Ternary Search Trees The Dictionary class is a specialized data structure storing all of the English words along with their definitions. Because some (if not most) words have multiple definitions, each word maps not to a single string but a Vector of them. The Dictionary is backed by a data structure called a ternary search tree . Ternary search trees are hybrids of two data structures we've studied extensively over the past two weeks: binary search trees, and tries. Binary trees are space efficient in that the amount of memory used is proportional to the number of entries it stores. Tries are exceptionally fast, because the time to look up, insert, or delete any one string is bounded by the length of the longest word in the dictionary, regardless of the dictionary’s size. Ternary search trees combine elements of the two. Like binary search trees, they are space efficient, except that its nodes have three children instead of two. Like tries, they proceed character by character during a search. A search compares the current character in the key to the letter embedded in a node. If the current character is less, the search continues along the less pointer. If the search character is greater, the search follows the greater pointer. If the characters match, then the search
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This note was uploaded on 01/13/2011 for the course CS 106X taught by Professor Cain,g during the Fall '08 term at Stanford.

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32-Section-Handout - CS106X Autumn 2010 Handout XX November...

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