CSC 207.02 2019S, Class 2^5: Hash tables

Overview

• Preliminaries
  • Notes and news
  • Upcoming work
  • Extra credit
  • Questions
• Quiz
• Hash tables: Key ideas
• An exercise: A simple hash function
• Analyzing efficiency
• From objects to integers
• Improving our hash function
• Complexities

Preliminaries

News / Etc.

• The computer ate today’s eboard. Sorry. Look at the eboard from CSC 207.02 for similar details.
• Today is a talk day. Sit where you would like.
• Apologies for continuing to be behind. I’m still not perfectly well, and sleep is trumping other issues.
• Copies of the skip list reading are available at the back of the room.

Upcoming work

• No additional reading! (But you may ant to review.)
• Assignment 8 due Thursday the 25th
• No lab writeup for today

Extra credit

Extra credit (Academic/Artistic)

• New: CS Table, Tomorrow, “The Cathedral and the Bazaar”
• PBK Convo, Thursday, 11am: “Antievolutionism in Historical Perspective”
• New: McKibben lecture, Thursday, 4:15 p.m., JRC 101

Extra credit (Peer)

• New/Questionable: Track and Field at Drake Relays and/or Grand View

Extra credit (Wellness)

Extra credit (Wellness, Regular)

• TODAY 30 Minutes of Mindfulness at SHACS/SHAW every Monday 4:15-4:45
• Any organized exercise. (See previous eboards for a list.)
• 60 minutes of some solitary self-care activities that are unrelated to academics or work. Your email reflection must explain how the activity contributed to your wellness.
• 60 minutes of some shared self-care activity with friends. Your email reflection must explain how the activity contributed to your wellness.

Extra credit (Misc)

• TONIGHT Public speaking workshop - April 22 at 7pm in HSSC S3325, with Kathy Clemons-Beasley ‘05.

Other good things

Questions

Quiz

Hash tables: Key ideas

An exercise: A simple hash function

A:1,  B:2,  C:3,  D:4,  E:5,  F:6,  G:7,  H:8,  I:9,  J:10, K:11, L:12, M:13, 
N:14, O:15, P:16, Q:17, R:18, S:19, T:20, U:21, V:22, W:23, X:24, Y:25, Z:26

0:                              10:                     20:
1:                              11:                     21:
2:                              12:                     22:
3:                              13:                     23:
4:                              14:                     24:
5:                              15:                     25:
6:                              16:                     26:
7:                              17:                     27:
8:                              18:                     28:
9:                              19:                     29:

Hash tables; Assessing costs

From objects to integers

Improving that hash function

Complexities