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Curricularizing the ACM... ?

Curricularizing the ACM... ?. Zach Dodds ~ November 13, 2010. Four undergraduate years ≈ 190 students each. Concrete mascot, Wally Wart. Every student must pass CS 1. Hard-won lesson #1: at HMC, if you want students to participate in something, curricularize it!.

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Curricularizing the ACM... ?

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  1. Curricularizing the ACM... ? Zach Dodds ~ November 13, 2010

  2. Four undergraduate years ≈ 190 students each Concrete mascot, Wally Wart Every student must pass CS 1 Hard-won lesson #1: at HMC, if you want students to participate in something, curricularize it!

  3. Our one-unit CS 189 class... Tuesdays 4:15-5:30 pm each week...

  4. Our one-unit CS 189 class... Hard-won lesson #2: at HMC, if you want students to participate in something, provide food!

  5. Running total of problems solved weekly problem sets of 4-6 problems... week 0 week 1 week 2 week 3 worth 2 points, if done by 10pm Tuesday; 1 point otherwise graded via a script that runs diff on our server Waterloo et al.!

  6. Short lectures 45 minutes every other Tuesday... Other meetings are lab sessions. No teaching credit for this, but good will credit == at least half the food! dynamic programming geometry Binary Search graphs

  7. This week: cow placement Output Input Number of cow stalls in the barn 8 Number of cows to put in the stalls 5 2 1 2 8 4 9 The largest minimum spacing possible after placing the cows The locations of stalls The barn! 1 2 4 8 9 how do we best fit 2 cows? 3 cows? 4?

  8. cowscode # get (N) # of stalls, (C) cows, and (S), the stalls N = input(); C = input(); S = []; foriinrange(N): S += [input()] # list o' stalls S.sort() # sort them! lo = 0 hi = max(S)-min(S)+1 while True: mid = (lo + hi)/2 # does anyone see the bug here? if mid == hi or mid == lo: break ifCHECKS_OUT( mid, C, S ): lo = mid # it worked! Look higher (set lo to mid) else: hi = mid # it didn't work Look lower (set hi to mid) print mid # output the result! input BS setup binary search

  9. This bug went undetected in Java's libraries for years...

  10. Our general strategy Give 75% of the code for one problem... • Everyone gets that problem, at least. • Everyone has a good start on the next problems that use binary search! Allow use of any language... Keep contest in perspective... If something isn't useful to all CS majors, we don't bother.

  11. ACM: a light hat to wear... Problems + Food = ACM class Lilian Andrew Thoughts... ?

  12. ACM today! Today: BS! Next 11/2: guest speaker... On 11/9: final lab session 11/13: regionals Nice work to everyone in the qualifiers and evening lab... On 11/16: wrap-up

  13. ACM this week!?

  14. Next week This talk is optional, but it should be good! In addition, it's incentivized @ 2 problems... It may count as a colloquium, too...

  15. Jotto! sophomores remain... Sophs Jrs Srs Profs pluot 1 pluot 2 pluot 1 pluot 2 squid 2 squid 1 squid 0 squid 1 fails 2 fails 2 fails 0 fails 2 cache 1 cache 2 cache 3 cache 0 china 0 china 1 china 3 china 2 quail 2 quail 1 quail 0 quail 3 conch 0 conch 0 conch 5 conch 1 laugh ? laugh 5 laugh x laugh 2

  16. Problem D from the 2009 World Finals in Stockholm:Pipe Packing Given a set of four wire diameters: What is the minimum diameter of pipe that can contain all four wires? (Constraint: pipes only come in millimeter sizes)

  17. A lower bound: sum of largest two wire-diameters An upper bound: sum of all four wire-diameters Intuition: Solve this problem by binary search • Binary search between lower bound and upper bound • Given a pipe diameter and four wire diameters, can you pack the wires inside the pipe? • Choose the smallest integer pipe diameter that fits

  18. Binary search in a sorted list... in Python What's next... ? we want to return True or False: is val in S?

  19. This week's problems… palpath city aggr cowset flood2 These three are all examples of problems for which binary search might be a good technique… could be used here, too...

  20. Problem D from the 2009 World Finals in Stockholm:Pipe Packing Given a set of four wire diameters: What is the minimum diameter of pipe that can contain all four wires? (Constraint: pipes only come in millimeter sizes)

  21. A lower bound: sum of largest two wire-diameters An upper bound: sum of all four wire-diameters Intuition: Solve this problem by binary search • Binary search between lower bound and upper bound • Given a pipe diameter and four wire diameters, can you pack the wires inside the pipe? • Choose the smallest integer pipe diameter that fits

  22. Enjoy! Thoughts... ?

  23. Last week: wifi Input Output 1.0 The # of test cases... 1 2 3 1 3 10 The smallest max distance achievable The # of access points and the # of houses Locations of the houses... 1 3 10

  24. This week: city # of people to house Output Input cost per unit distance from (0,0) 194 maximum # of stories per building 10 20 3 11 22 33 The minimium cost to house the specified # of people 0dist cost of 1st story 1dist 0dist 0dist 1dist 1dist 0dist 1dist 2dist 3dist the central station where everyone works is at (0,0) distances to it are considered to be |x|+|y|-1

  25. This week: cowset # of cows available, up to 34 Output Input minimum ID sum 5 maximum ID sum 3 -1 2 1 -2 3 The number of subsets whose IDs sum between min and max ID # for 1st cow Try all subsets...? ID # for 2nd cow ID # for 3rd cow Farmer Ran is willing to play frisbee with any subset of cows whose IDs sum to any value between the min and max...

  26. This week: cowset # of cows available, up to 34 Output Input minimum ID sum 5 maximum ID sum 3 -1 2 1 -2 3 The number of subsets whose IDs sum between min and max ID # for 1st cow Takes too long to try all subsets...! ID # for 2nd cow How could Bin Search speed it up? ID # for 3rd cow Farmer Ran is willing to play frisbee with any subset of cows whose IDs sum to any value between the min and max...

  27. Try this week's problems! Perhaps start with aggr...

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