1 / 13

David Evans cs.virginia/evans

Lecture 11: Sorting Grounds and Bubbles. David Evans http://www.cs.virginia.edu/evans. Coffee Bean Sorting in Guatemala. CS200: Computer Science University of Virginia Computer Science. Menu. Find Most Sorting. find-most-caffeinated. (define (find-most-caffienated menu) (insertl

amandaamy
Download Presentation

David Evans cs.virginia/evans

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Lecture 11: Sorting Grounds and Bubbles David Evans http://www.cs.virginia.edu/evans Coffee Bean Sorting in Guatemala CS200: Computer Science University of Virginia Computer Science

  2. Menu • Find Most • Sorting CS 200 Spring 2003

  3. find-most-caffeinated (define (find-most-caffienated menu) (insertl (lambda (c1 c2) (if (> (coffee-caffeine-rating c1) (coffee-caffeine-rating c2)) c1 c2)) menu (make-coffee “water” 0.00 0))) ;; we should only water if there are no coffees ;; on the menu CS 200 Spring 2003

  4. find-most-caffeinated (define (find-most-caff menu) (if (null? menu) (make-coffee “water" 0.00 0) (let ((rest-most-caff (find-most-caff (cdr menu)))) (if (> (coffee-caffeine-rating (car menu)) (coffee-caffeine-rating rest-most caff)) (car menu) rest-most-caff)))) CS 200 Spring 2003

  5. Comparing Processes > (trace >) (>) > (find-most-caff todays-menu) |(> 57 -1) |#t |(> 15 57) |#f |(> 12 57) |#f |(> 92 57) |#t |(> 85 92) |#f ("BEN'S Expresso Noir Supreme" 17.23 . 92) > (find-most-caffienated todays-menu) |(> 57 -1) |#t |(> 15 57) |#f |(> 12 57) |#f |(> 92 57) |#t |(> 85 92) |#f ("BEN'S Expresso Noir Supreme" 17.23 . 92) CS 200 Spring 2003

  6. Sorting CS 200 Spring 2003

  7. Simple Sorting • We know how to find-most-caffeinated • How do we sort list by caffeine rating? • Use (find-most-caffeinated menu) to find the most caffeinated • Remove it from the menu • Repeat until the menu is empty CS 200 Spring 2003

  8. Delete ;;; Evaluates to the list parameter with ;;; first instance of el removed. (define (delete lst el) (if (null? lst) (error "Element not found!") (if (eq? (car lst) el) (cdr lst) (cons (car lst) (delete (cdr lst) el))))) CS 200 Spring 2003

  9. sort-menu (define (sort-menu menu) (if (null? menu) menu (let ((most-caff (find-most-caffeinated menu))) (cons most-caff (sort-menu (delete menu most-caff)))))) How can we generalize this? (e.g., sort by price also) CS 200 Spring 2003

  10. All Sorts (define (sort cf lst) (if (null? lst) lst (let ((most (find-most cf lst))) (cons most (sort cf (delete lst most)))))) CS 200 Spring 2003

  11. Caffeine Sorts (define (sort-menu-by-caffeine menu) (sort (lambda (c1 c2) (> (coffee-caffeine-rating c1) (coffee-caffeine-rating c2))) menu)) CS 200 Spring 2003

  12. find-most (define (find-most cf lst) (insertl (lambda (c1 c2) (if (cf c1 c2) c1 c2)) lst (car lst))) CS 200 Spring 2003

  13. Charge • PS3 Due Wednesday • Lab Hours: Tonight, 6-7:30 PM in Small Hall • Think about faster ways of sorting (next time) • Read Tyson’s essay (before Friday) • How does it relate to  (n2) • How does it relate to grade inflation CS 200 Spring 2003

More Related