PFTD APT-3 due Tuesday, September 22 Assignment 2 due September 29 - - PowerPoint PPT Presentation

Compsci 101 Pancakes, While loops, Parallel Lists Live Lecture

9/17/2020 Compsci 101, Fall 2020 1

Susan Rodger September 17, 2020

J is for …

• JSON
• Format for data

transmitted across the web

• JPEG
• Image format based on

lossy compression

• Jacquard Loom
• 1804 "automated" loom

9/17/2020 Compsci 101, Fall 2020 2

Announcements

• APT-3 due Tuesday, September 22
• Assignment 2 due September 29
• Last Chance for Accommodations letter
• Email to Yesenia at yvelasco@cs.duke.edu
• Do not email Prof. Rodger!
• No Videos, RQ’s next week
• Exam 1 Thursday 9/24
• Pick a time and take it that day
• Fixed amount of time to take it
• APT Quiz 1 9/25-9/28

9/17/2020 Compsci 101, Fall 2020 3

PFTD

• Files and Data
• Pancake APT
• While loops and Collatz sequence
• Parallel lists

9/17/2020 Compsci 101, Fall 2020 4

WOTO-1 Files http://bit.ly/101f20-0917-1

• In your groups:
• Come to a consensus

9/17/2020 Compsci 101, Fall 2020 6

Pancakes!

9/17/2020 Compsci 101, Fall 2020 7

APT Pancake

• How do you solve this (or any) problem?
• 7 Steps!
• Some APTs are hard problems to solve (step 1-4)
• Translating to code easy
• Some APTs have easy-to-see algorithms (step 5)
• Translating to code is hard

9/17/2020 Compsci 101, Fall 2020 8 compsci 101, fall 2017 9

compsci 101, fall 2017 10

WOTO-2 Pancakes http://bit.ly/101f20-0917-2

• In your groups:
• Come to a consensus

9/17/2020 Compsci 101, Fall 2020 14

Let’s code it up!

9/17/2020 Compsci 101, Fall 2020 25

Review: While Loops

• Don't know: how many times loop executes
• a priori knowledge, we'll know afterword
• Do know: condition that should be true after loop
• Its negation is the expression for

BOOL_CONDITION (loop guard)

9/17/2020 Compsci 101, Fall 2020 28

while BOOL_CONDITION: LOOP_BODY # modify variables, affect expression

WOTO-3 Collatz and While http://bit.ly/101f20-0917-3

• In your groups:
• Come to a consensus

9/17/2020 Compsci 101, Fall 2020 29

Genesis Bond ‘16

• Facebook Engineer
• Struggled at Duke
• 5 years
• Dismissed 1 semester due

to grades

• Revature
• Trainer Full Stack

Development

• http://bit.ly/dukebond

9/17/2020 Compsci 101, Fall 2020 30

Poor preparation promotes poor performance. In anything you do, your preparation will show.

Parallel Lists Review

• We will use parallel lists to track data
• Each word is stored in a list named words
• Word’s count is stored in a list named counts
• # occurrences of words[k] is in counts[k]

["apple", "fox", "vacuum", "lime"] [5,2,25,15]

• What happens when we read a word?

9/17/2020 Compsci 101, Fall 2020 31

WOTO-4 File Frequency http://bit.ly/101f20-0917-4

• In your groups:
• Come to a consensus

9/17/2020 Compsci 101, Fall 2020 32