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Locators - Locators 8:45 AM Outline and Reading 3a...

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4/1/2003 8:45 AM Locators 1 Locators 3 a 1 g 4 e 4/1/2003 8:45 AM Locators 2 Outline and Reading Locators (§7.4, §9.6) Locator-based methods (§7.4.1) Implementation Positions vs. Locators 4/1/2003 8:45 AM Locators 3 Locators A locators identifies and tracks a (key, element) item within a data structure A locator sticks with a specific item, even if that element changes its position in the data structure Intuitive notion: claim check reservation number Methods of the locator ADT: key (): returns the key of the item associated with the locator element (): returns the element of the item associated with the locator Application example: Orders to purchase and sell a given stock are stored in two priority queues (sell orders and buy orders) the key of an order is the price the element is the number of shares When an order is placed, a locator to it is returned Given a locator, an order can be canceled or modified 4/1/2003 8:45 AM Locators 4 Locator-based Methods Locator-based priority queue methods: insert (k, o): inserts the item
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