Unordered Data Structures: Sets and Maps, Summaries of Data Structures and Algorithms

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Unordered Data Structures:

Sets and Maps

What’s an example of “unordered data” that you’ve

encountered in your life?

(put your answers the chat)

vectors + grids

stacks + queues

sets + maps

Object-Oriented Programming

arrays

dynamic memory management

linked data structures

algorithmic testing analysis

recursive problem-solving

Roadmap

Life after CS106B!

C++ basics

Diagnostic

real-world algorithms

Core Tools

User/client Implementation

Object-Oriented Programming

arrays

dynamic memory management

linked data structures

algorithmic testing analysis

recursive problem-solving

Roadmap

Life after CS106B!

C++ basics

Diagnostic

real-world algorithms

Core Tools

Implementation

vectors + grids

stacks + queues

sets + maps

User/client

Today’s

question

When is it appropriate to

use different types of

unordered data structures?

Review

(grids and queues and stacks, oh my!)

What is a grid?

● A 2D array, defined with a particular width and height

● Useful for spreadsheets, game boards, etc.

● Three ways to declare a grid ○ Grid gridName; ○ Grid gridName(numRows, numCols); ○ Grid gridName = {{r0c0, r0c1, r0c2}, {r1c0, r1c1, r1c2},...};

● We could use a combination of Vectors to simulate a 2D matrix, but a Grid is easier!

a0 a1 a

b0 b1 b

c0 c1 c

The GridLocation struct

● A pre-defined struct in the Stanford C++ libraries that makes it more convenient to store Grid locations

● To declare a struct, you can either assign each of its members separately or assign it when it’s created:

GridLocation origin = {0, 0}; GridLocation origin; origin.row = 0; origin.col = 0;

struct GridLocation { int row; int col; }

What is a queue?

● Like a real queue/line!

● F irst person I n is the F irst person O ut (FIFO) ○ When you remove (dequeue) people from the queue, you remove them from the front of the line.

● Last person in is the last person served ○ When you insert (enqueue) people into a queue, you insert them at the back (the end of the line).

Ordered ADTs with accessible

indices

Types:

● Vectors (1D) ● Grids (2D)

Traits:

● Easily able to search through all elements ● Can use the indices as a way of structuring the data

Ordered ADTs where you can’t

access elements by index

Types:

● Queues (FIFO) ● Stacks (LIFO)

Traits:

● Constrains the way you can insert and access data ● More efficient for solving specific LIFO/FIFO problems

Activity:

towersOfHanoi()

Towers of Hanoi

● Rules: ○ Can only move one disk at a time ○ You cannot place a larger disk on top of a smaller disk

Discuss : How would

you solve this problem?

[breakout rooms]

Pseudocode

(1) Move disk 1 to destination (2) Move disk 2 to auxiliary (3) Move disk 1 to auxiliary (4) Move disk 3 to destination

(5) Move disk 1 to source (6) Move disk 2 to destination (7) Move disk 1 to destination

Code the solution for

three disks!

[breakout rooms]