Chapter 3 Pointers and ArrayBased Lists Data Structures

Chapter 3 Pointers and Array-Based Lists Data Structures Using C++ 1

Chapter Objectives • Learn about the pointer data type and pointer variables • Explore how to declare and manipulate the pointer variables • Learn about the address of operator and dereferencing operator • Discover dynamic variables • Examine how to use the new and delete operators to manipulate dynamic variables Data Structures Using C++ 2

Chapter Objectives • Learn about pointer arithmetic • Discover dynamic arrays • Become aware of the shallow and deep copies of data • Discover the peculiarities of classes with pointer data members • Explore how dynamic arrays are used to process lists Data Structures Using C++ 3

Pointer Data Types and Pointer Variables • Pointer variable: variable whose content is a memory address • Syntax to declare pointer variable: data. Type *identifier; • Address of operator: Ampersand, & • Dereferencing operator: Asterisk, * Data Structures Using C++ 4

Pointers • Statements: int *p; int num; Data Structures Using C++ 5

Pointers Data Structures Using C++ 6

Pointers Data Structures Using C++ 7

Pointers Data Structures Using C++ 8

Pointers • Summary of preceding diagrams – &p, p, and *p all have different meanings – &p means the address of p – p means the content of p – *p means the content pointed to by p, that is pointed to by the content of memory location Data Structures Using C++ 9

Pointers Data Structures Using C++ 10

Pointers x = 50; p = &x; Data Structures Using C++ 11

Pointers *p = 38; Data Structures Using C++ 12

Classes, structs, and Pointer Variables The syntax for accessing a class (struct) member using the operator -> is pointer. Variable. Name->class. Member. Name Therefore, the statement (*student. Ptr). gpa = 3. 9; is equivalent to the statement student. Ptr->gpa = 3. 9; Data Structures Using C++ 13

Classes, structs, and Pointer Variables Data Structures Using C++ 14

Classes, structs, and Pointer Variables Data Structures Using C++ 15

Syntax to use operator new data. Type; new data. Type[int. Exp]; variables //to allocate a single variable //to allocate an array of Data Structures Using C++ 16

Syntax to use operator delete pointer; delete [] pointer; //to destroy a single dynamic variable //to destroy a dynamically created array Data Structures Using C++ 17

Operations on pointer variables • Assignment operations • Relational operations • Limited arithmetic operations Data Structures Using C++ 18

Functions and Pointers void example(int* &p, double *q) {. . . } Data Structures Using C++ 19

Pointers and Function Return Pointers int* test. Exp(. . . ) {. . . } is a pointer of the type int. Data Structures Using C++ 20

Shallow Versus Deep Copy and Pointers Data Structures Using C++ 21

Shallow Versus Deep Copy and Pointers Data Structures Using C++ 22

Shallow Versus Deep Copy and Pointers second = new int[10]; for(int j = 0; j < 10; j++) second[j] = first[j]; Data Structures Using C++ 23

Classes and Pointers: Some Peculiarities class pointer. Data. Class { public: . . . private: int x; int len. P; int *p; }; pointer. Data. Class object. One; pointer. Data. Class object. Two; Data Structures Using C++ 24

Classes and Pointers: Some Peculiarities Data Structures Using C++ 25

Destructor Data Structures Using C++ 26

Destructor pointer. Data. Class: : ~pointer. Data. Class() { delete [ ] p; } class pointer. Data. Class { public: ~pointer. Data. Class(); . . . private: int x; int len. P; int *p; }; Data Structures Using C++ 27

Assignment Operator Data Structures Using C++ 28

Assignment Operator Data Structures Using C++ 29

Assignment Operator Data Structures Using C++ 30

Overloading the Assignment Operator Function Prototype (to be included in the definition of the class): const class. Name& operator=(const class. Name&); Function Definition: const class. Name& class. Name: : operator=(const class. Name& right. Object) { //local declaration, if any if(this != &right. Object) //avoid self-assignment { //algorithm to copy right. Object into this object } //return the object assigned return *this; } Data Structures Using C++ 31

Overloading the Assignment Operator • Definition of function operator=: – Only one formal parameter – Formal parameter generally const reference to particular class – Return type of function is reference to particular class Data Structures Using C++ 32

Copy Constructor Data Structures Using C++ 33

Copy Constructor Data Structures Using C++ 34

Copy Constructor Data Structures Using C++ 35

Copy Constructor • If a class has pointer data members: – During object declaration, the initialization of one object using the value of another object would lead to a shallow copying of the data if the default memberwise copying of data is allowed – If, as a parameter, an object is passed by value and the default member-wise copying of data is allowed, it would lead to a shallow copying of the data Data Structures Using C++ 36

Copy Constructor • The copy constructor automatically executes in the following situations – When an object is declared and initialized by using the value of another object – When, as a parameter, an object is passed by value – When the return value of a function is an object Data Structures Using C++ 37

Copy Constructor Data Structures Using C++ 38

Copy Constructor General syntax to include the copy constructor in the definition of a class: class. Name(const class. Name& other. Object); Data Structures Using C++ 39

Classes with Pointer Data Members • Include destructor in the class • Overload assignment operator for class • Include copy constructor Data Structures Using C++ 40

Overloading Array Index (Subscript) Operator ([ ]) Syntax to declare the operator function operator [ ] as a member of a class for nonconstant arrays: Type& operator[](int index); Syntax to declare the operator function operator [ ] as a member of a class for constant arrays: const Type& operator[](int index) const; Data Structures Using C++ 41

Array-Based Lists • List: A collection of elements of the same type • Length of list is number of elements in list Data Structures Using C++ 42

Operations performed on a list • • • Create the list; initialized to an empty state Determine whether the list is empty Determine whether the list is full Find the size of the list Destroy, or clear, the list Determine whether an item is the same as a given list element Data Structures Using C++ 43

Operations performed on a list • Insert an item in the list at the specified location • Remove an item from the list at the specified location • Replace an item at the specified location with another item • Retrieve an item from the list at the specified location • Search the list for a given item Data Structures Using C++ 44

UML Diagram of the class array. List. Type Data Structures Using C++ 45

Time Complexity of List Operations Data Structures Using C++ 46

Chapter Summary • • Pointer data types and variables Dynamic variables Pointer arithmetic Dynamic arrays Shallow and deep copying Peculiarities of classes with pointer data members Processing lists Data Structures Using C++ 47