aps105 lists. structures arrays allow a collection of elements –all of the same type how to...

APS105

Lists

Structures

Structures

• Arrays allow a collection of elements– All of the same type

• How to collect elements of different types?– Structures; in C: struct

• General form:

struct { <variable declarations> } <identifier list>;

Example• A struct of stock items at a store:

.

Separate Definition from Declaration

.

Using Typedef

• Can define your own types using typedef!• General form:

typedef <type> <yourTypeName>;• Examples:

.

Doing typedef and definition at once:

.

Referencing Struct Members

.

Structs and Pointers

StockItem x;StockItem *p;p = &x; // p points to x

// ways to set quantity to 500:.

Malloc a Struct (StockItem)

.

Lists

Intro

• A list is a sequence of items– can implement lists different ways:

• a group of variables• an array• using pointers (as we will see)

• Typical list operations– start a new, empty list– insert a new element into the list– find an item with a certain value in the list– delete an item from the list– print the list

• Abstract Data Type (ADT)– A list is an example of an ADT– An ADT is a concept– there are multiple ways to implement an ADT

The Problem with Arrays

• Insert an item into the middle of the list:

• Delete an item from the middle of the list:

• What if the array isn’t big enough?

5 3 1 6 2 6 7 0

9

5 3 1 6 2 6 7 0

X

5 3 1 6 2 6 7 3 8 0

9

Flexible List: “Linked List”

• Insert an item into the middle of the list:

• Delete an item from the middle of the list:

9

5 3 1 6 2 6 7

5 3 1 6 2 6 7

X

5 3 1 6 2 6 7

Implementing a Linked List of ints

.

Allocating a new Node

• a function to allocate & initialize a node

.

Creating a List: Adding to the end

.

Creating a List: Adding to the front

.

Function to Print a List

.

Deleting the First Node of a List

info: 5link:

myListinfo: 3link:

info: 1link:

Function to Delete first Node

.

Delete first Node: return new head

.

Function to return true if an item found

.

Function to Delete Entire List

.

Function to Add Element to End of List

.

Deleting the Last Node of a List

info: 5link:

myListinfo: 3link:

info: 1link:

Function to Delete Last Element

.

Inserting into an Ordered List

info: 1link:

myListinfo: 3link:

info: 5link:

4

Function to Insert into Ordered List.

Using Recursion on Lists

Printing a List using Recursion• can think of a list recursively as: a head node plus a list

.

Deleting a List using Recursion.

Finding an Item using Recursion.

Compare 2 Lists: true if identical.

Insert into an Ordered List.