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1
C++ Plus Data Structures
Nell Dale
Lecture 2
Slides by Sylvia Sorkin, Community College of Baltimore County - Essex Campus
Modified by Reneta Barneva - SUNY Fredonia
2
Data Abstraction
Separation of a data type’s logical properties from its implementation.
LOGICAL PROPERTIES IMPLEMENTATION
What are the possible values? How can this be done in C++?
What operations will be needed? How can data types be used?
3
APPLICATION
0 0 0 0 0 0 0 0 0 0 0 1 1 0 0 1
REPRESENTATION
Data Encapsulation
is the separation of the representation of data from the applications that use the data at a logical level; a programming language feature that enforces information hiding.
int y;
y = 25;
4
Encapsulated C++ Data Type int
Value range: INT_MIN . . INT_MAX
Operations: + prefix - prefix + infix - infix * infix / infix % infixRelational Operators infix
TYPE int
(inside)
Representation of
int
as 16 bits two’s complement
+
Implementation of Operations
5
Abstract Data Type (ADT)
A data type whose properties (domain and operations) are specified independently of any particular implementation.
6
Application (or user) level: modeling real-life data in a specific context.
Logical (or ADT) level: abstract view of the domain and operations. WHAT
Implementation level: specific representation of the structure to hold the data items, and the coding for operations. HOW
Data from 3 different levels
7
Viewing a library from 3 different levels
Application (or user) level: Library of Congress, or Baltimore County Public Library.
Logical (or ADT) level: domain is a collection of books; operations include: check book out, check book in, pay fine, reserve a book.
Implementation level: representation of the structure to hold the “books”, and the coding for operations.
8
Composite Data Type
A composite data type is a type which
stores a collection of individual data components under one variable name,
and allows the individual data components to be accessed.
4 Basic Kinds of ADT Operations
Constructor -- creates a new instance (object) of an ADT.
Transformer -- changes the state of one or more of the data values of an instance.
Observer -- allows us to observe the state of one or more of the data values without changing them.
Iterator -- allows us to process all the components in a data structure sequentially.
9
Two Forms of Composite Data Types
Components are not organized with respect to one another.
The organization determines method used to access individual data components.
UNSTRUCTURED STRUCTURED
EXAMPLES: EXAMPLES: arraysclasses and structs
10
11
C++ Built-In Data TypesC++ Built-In Data Types
Composite
array struct union class
Address
pointer reference
Simple
Integral Floating
char short int long enum
float double long double
12
Records
A record is a composite data type made up of a finite collection of not necessarily homogeneous elements called members or fields. For example . . .
.year 1999
.maker ‘h’ ‘o’ ‘n’ ‘d’ ‘a’ ‘\0’ . . .
.price 18678.92
thisCar at Base Address 6000
13
struct CarType
struct CarType{
int year ; char maker[10];
float price ;
} ;
CarType thisCar; //CarType variables
CarType myCar;
14
Accessing struct members
The member selection operator (period . ) is used between the variable name and the member identifier to access individual members of a record (struct or class) type variable.
EXAMPLES
myCar.year
thisCar.maker[4]
15
Valid struct operations
Operations valid on an entire struct type variable:
assignment to another struct variable of same type,
pass as a parameter to a function
(either by value or by reference),
return as the value of a function.
Pass-by-value
CALLINGBLOCK
FUNCTION CALLED
sends a copy of the contents of the actual parameter
SO, the actual parameter cannot be changed by the function.
16
Pass-by-reference
sends the location (memory address)of the actual parameter
can change value ofactual parameter
CALLINGBLOCK FUNCTION
CALLED
17
18
Using struct type Reference Parameter to change a member
void AdjustForInflation(CarType& car, float perCent)
// Increases price by the amount specified in perCent{
car.price = car.price * perCent + car.price;
} ;
SAMPLE CALL
AdjustForInflation(myCar, 0.03);
19
Using struct type Value Parameter to examine a member
bool LateModel(CarType car, int date)
// Returns true if the car’s model year is later than or// equal to date; returns false otherwise.{
return ( car.year >= date ) ;
} ;
SAMPLE CALL
if ( LateModel(myCar, 1995) )cout << myCar.price << endl ;
20
C++ class data type
A class is an unstructured type that encapsulates a fixed number of data components (data members) with the functions (called member functions) that manipulate them.
The predefined operations on an instance of a class are whole assignment and component access.
21
class DateType Specification
// SPECIFICATION FILE ( datetype.h )
class DateType // declares a class data type{
public : // 4 public member functions
void Initialize ( int newMonth , int newDay , int newYear ) ;int YearIs( ) const ; // returns yearint MonthIs( ) const ; // returns monthint DayIs( ) const ; // returns day
private : // 3 private data members
int year ; int month ; int day ;
} ;21
22
Use of C++ data type class
Variables of a class type are called objects (or instances) of that particular class.
Software that declares and uses objects of the class is called a client.
Client code uses public member functions (called methods in OOP) to handle its class objects.
Sending a message means calling a public member function.
23
Client Code Using DateType#include “datetype.h” // includes specification of the class#include “bool.h”
int main ( void ){
DateType startDate ; // declares 2 objects of DateType DateType endDate ; bool retired = false ;
startDate.Initialize ( 6, 30, 1998 ) ; endDate.Initialize ( 10, 31, 2002 ) ;
cout << startDate.MonthIs( ) << “/” << startDate.DayIs( ) << “/” << startDate.YearIs( ) << endl;
while ( ! retired ) { finishSomeTask( ) ; . . . } }
23
24
2 separate files generally used for class type
// SPECIFICATION FILE ( datetype .h ) // Specifies the data and function members. class DateType { public: . . .
private: . . . } ;
// IMPLEMENTATION FILE ( datetype.cpp ) // Implements the DateType member functions.
. . .
25
DateType Class Instance Diagrams
Initialize
YearIs
MonthIs
DayIs
startDate endDate
Private data:
year
month
day
2002
10
31
Initialize
YearIs
MonthIs
DayIs
1998
6
30
Private data:
year
month
day
26
Implementation of DateType member functions
// IMPLEMENTATION FILE (datetype.cpp)
#include “datetype.h” // also must appear in client code
void DateType :: Initialize ( int newMonth, int newDay,
int newYear )
// Post: year is set to newYear.
// month is set to newMonth.
// day is set to newDay.
{
year = newYear ;
month = newMonth ;
day = newDay ;
}26
int DateType :: MonthIs ( ) const
// Accessor function for data member month
{
return month ;
}
int DateType :: YearIs ( ) const
// Accessor function for data member year
{
return year ;
}
int DateType :: DayIs ( ) const
// Accessor function for data member day
{
return day ;
} 27
28
Familiar Class Instances and Member Functions
The member selection operator ( . ) selects either data members or member functions.
Header files iostream.h and fstream.h declare the istream, ostream,and ifstream, ofstream I/O classes.
Both cin and cout are class objects and get and ignore
are member functions.cin.get (someChar) ;
cin.ignore (100, ‘\n’) ;
These statements declare myInfile as an instance of class ifstream and invoke member function open.
ifstream myInfile ;
myInfile.open ( “A:\\mydata.dat” ) ;
29
Scope Resolution Operator ( :: ) C++ programs typically use several class types.
Different classes can have member functions with the same identifer, like Write( ).
Member selection operator is used to determine the class whose member function Write( ) is invoked.
currentDate .Write( ) ; // class DateType
numberZ .Write( ) ; // class ComplexNumberType
In the implementation file, the scope resolution operator is used in the heading before the member function’s name to specify its class.
void DateType :: Write ( ) const{ . . .
}
30
Information Hiding
Class implementation details are hidden from the client’s view. This is called information hiding.
Public functions of a class provide the interface between the client code and the class objects.
clientcode
specification implementation
abstraction barrier
// SPECIFICATION FILE ( strtype.h )#include <fstream.h>#include <iostream.h>
const int MAX_CHARS = 200 ;enum RelationType { LESS, EQUAL, GREATER } ;enum InType { ALPHA_NUM, ALPHA, NON_WHITE, NOT_NEW } ;
class StrType // declares class data type{public : // 7 public member functions
void MakeEmpty ( ) ; void GetString ( bool skip, InType charsAllowed ) ;
void GetStringFile ( bool skip, InType charsAllowed, ifstream& inFile ) ;
void PrintToScreen ( bool newLine ) const ; void PrintToFile ( bool newLine, ofstream& outFile) const ;
int LengthIs( ) const ; void CopyString( StrType& newString ) const ;
private : // 1 private data memberchar letters [MAX_CHARS + 1 ] ;
} ; 31
32
StrType Class Interface Diagram
StrType class
Private data:
letters
GetString
GetStringFile
CopyString
LengthIs
PrintToFile
MakeEmpty
PrintToScreen‘c’ ’a’ ’t’ ’\0’ ...
33
Multifile C++ Programs
C++ programs often consist of several different files with extensions such as .h and .cpp
related typedef statements, const values, enum type declarations, and similar items are often placed in user-written header files
by using the #include preprocessor directive the contents of these header files are inserted into any program file that uses them
34
Inserting Header Files
#include <iostream> // iostream
#include “school.h”
int main ( )
{ enum SchoolType
{ PRE_SCHOOL,
. ELEM_SCHOOL, .
MIDDLE_SCHOOL,. HIGH_SCHOOL, COLLEGE } ;
}
// IMPLEMENTATION FILE (strtype.cpp)
#include “strtype.h” // also appears in client code
#include “string.h”
void StrType :: MakeEmpty ( )
// Post: letters is empty string.
{
letters[0] = ‘\0’ ;
}
. . .
int StrType :: LengthIs ( ) const
// Returns length of letters string.
{
return strlen ( letters ) ;
} 35
36
One-Dimensional Array at the Logical Level
A one-dimensional array is a structured composite data type made up of a finite, fixed size (known at compile time) collection of homogeneous (all of the same data type) elements having relative positions and to which there is direct access (any element can be accessed immediately).
Array operations (creation, storing a value, retrieving a value) are performed using a declaration and indexes.
37
Implementation Example
float values[5]; // assume element size is 4 bytes
This ACCESSING FUNCTION gives position of values[Index]
Address(Index) = BaseAddress + Index * SizeOfElement
Base Address
values[0] values[1] values[2] values[3] values[4]
7000 7004 7008 7012 7016
Indexes
38
One-Dimensional Arrays in C++
The index must be of an integral type (char, short, int, long, or enum).
The index range is always 0 through the array size minus 1.
Arrays cannot be assigned, and cannot be the return type of a function.
39
Another Example
char name[10]; // assume element size is 1 byte
name[0] name[1] name[2] name[3] name[4] . . . . . name[9]
6000 6001 6002 6003 6004 6005 6006 6007 6008 6009
Base Address
This ACCESSING FUNCTION gives position of name[Index]
Address(Index) = BaseAddress + Index * SizeOfElement
40
Passing Arrays as Parameters
In C++, arrays are always passed by reference, and & is not used with the formal parameter type.
Whenever an array is passed as a parameter, its base address is sent to the called function.
41
const array parameter
Because arrays are always passed as reference parameters, you can protect the actual parameter from unintentional changes by using const in formal parameter list and function prototype.
FOR EXAMPLE . . . // prototype
float SumValues( const float values[ ],
int numOfValues );
float SumValues (const float values[ ], int numOfValues )
// Pre: values[ 0] through values[numOfValues-1]
// have been assigned
// Returns the sum of values[0] through
// values[numOfValues-1]
{
float sum = 0;
for ( int index = 0; index < numOfValues; index++ )
{
sum += values [ index ] ;
}
return sum;
}
42
43
Two-Dimensional Array at the Logical Level
A two-dimensional array is a structured composite data type made up of a finite, fixed size collection of homogeneous elements having relative positions and to which there is direct access.
Array operations (creation, storing a value, retrieving a value) are performed using a declaration and a pair of indexes (called row and column) representing the component’s position in each dimension.
44
EXAMPLE -- To keep monthly high temperatures for 50 states in a two-dimensional array.
const int NUM_STATES = 50 ;
const int NUM_MONTHS = 12 ;
int stateHighs [ NUM_STATES ] [ NUM_MONTHS ] ;
[ 0 ]
[ 1 ]
[ 2 ]
.
. stateHighs [2] [7]
.
[ 48 ]
[ 49 ]
[0] [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11]
66 64 72 78 85 90 99 115 98 90 88 80row 2,col 7might beArizona’shigh forAugust
45
Finding the average high temperature for Arizona
int total = 0 ;
int month ;
int average ;
for ( month = 0 ; month < NUM_MONTHS ; month ++ )
total = total + stateHighs [ 2 ] [ month ] ;
average = int ( total / 12.0 + 0.5 ) ;
46
const int NUM_STATES = 50 ;const int NUM_MONTHS = 12 ;int stateHighs [ NUM_STATES ] [ NUM_MONTHS ] ;
In memory, C++ stores arrays in row order. The first row is followed by the second row, etc.
12 highs for state 0 12 highs for state 1 etc. Alabama Alaska first row second row
8000 8024 8048
Base Address
STORAGE
. . .
rows columns
47
Implementation Level ViewstateHighs[ 0 ] [ 0 ]stateHighs[ 0 ] [ 1 ]stateHighs[ 0 ] [ 2 ]stateHighs[ 0 ] [ 3 ]stateHighs[ 0 ] [ 4 ]stateHighs[ 0 ] [ 5 ]stateHighs[ 0 ] [ 6 ]stateHighs[ 0 ] [ 7 ]stateHighs[ 0 ] [ 8 ]stateHighs[ 0 ] [ 9 ]stateHighs[ 0 ] [10 ]stateHighs[ 0 ] [11 ]stateHighs[ 1 ] [ 0 ]stateHighs[ 1 ] [ 1 ]stateHighs[ 1 ] [ 2 ]stateHighs[ 1 ] [ 3 ] . . .
To locate an element such asstateHighs [ 2 ] [ 7] the compiler needs to know that there are 12 columnsin this two-dimensional array.
At what address will stateHighs [ 2 ] [ 7 ] be found?
Assume 2 bytes for type int.
Base Address 8000
48
Two-Dimensional Array Parameters
Just as with a one-dimensional array, when a two- (or higher) dimensional array is passed as a parameter, the base address of the actual array is sent to the function.
The size of all dimensions except the first must be included in the function heading and prototype.
The sizes of those dimensions for the formal parameter must be exactly the same as in the actual array.
49
const int NUM_STATES = 50 ;
const int NUM_MONTHS = 12 ;
int stateHighs [ NUM_STATES ] [ NUM_MONTHS ] ;
int stateAverages [ NUM_STATES ] ;
[ 0 ]
? [ 1 ]
? [ 2 ]
.
.
.
[ 48 ]
[ 49 ]
[0] [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11]
43 42 50 55 60 78 79 80 77 72 63 4066 64 72 78 85 90 99 115 98 90 88 80
Use the two-dimensional stateHighs array to fill a one-dimensional stateAverages array
Alaska
Arizona
void findAverages ( const int stateHighs [ ] [ NUM_MONTHS] , int stateAverages [ ] )
// Pre: stateHighs[ 0..NUM_STATES-1] [ 0..NUM_MONTHS-1] assigned
// Post: stateAverages[ 0..NUM_STATES-1 ] contains rounded average
// high temperature for each state{
int state;
int month;
int total;
for ( state = 0 ; state < NUM_STATES; state++ ) {
total = 0 ;
for ( month = 0 ; month < NUM_MONTHS ; month++ )
total += stateHighs [ state ] [ month ] ;
stateAverages [ state ] = int ( total / 12.0 + 0.5 ) ; }
}50
51
Using typedef with arrays
helps eliminate the chances of size mismatches between
formal and actual parameters. FOR EXAMPLE,
typedef int StateHighsType [ NUM_STATES ] [ NUM_MONTHS ] ;
typedef int StateAveragesType [ NUM_STATES ] ;
void findAverages( const StateHighsType stateHighs , StateAveragesType stateAverages )
{ . . .
}51
52
Declaring Multidimensional Arrays
EXAMPLE USING TYPEDEF
const int NUM_DEPTS = 5 ; // mens, womens, childrens, electronics, linens
const int NUM_MONTHS = 12 ;
const int NUM_STORES = 3 ; // White Marsh, Owings Mills, Towson
typedef long MonthlySalesType [NUM_DEPTS] [NUM_MONTHS] [NUM_STORES];
MonthlySalesType monthlySales;
const int NUM_DEPTS = 5 ; // mens, womens, childrens, electronics, linens
const int NUM_MONTHS = 12 ;
const int NUM_STORES = 3 ; // White Marsh, Owings Mills, Towson
typedef long MonthlySalesType [NUM_DEPTS] [NUM_MONTHS] [NUM_STORES] ;
MonthlySalesType monthlySales;
monthlySales[3][7][0]sales for electronics in August at White Marsh
12 MONTHS columns
5 D
EP
TS
ro
ws
3 STORES
sheets
53
54
More about Array Index
array index can be any integral type. This includes char and enum types
it is programmer’s responsibility to make sure that an array index does not go out of bounds. The index must be within the range 0 through the declared array size minus one
using an index value outside this range causes the program to access memory locations outside the array. The index value determines which memory location is used
55
Enumeration Types
C++ allows creation of a new simple type by listing (enumerating) all the ordered values in the domain of the type
EXAMPLE
enum MonthType { JAN, FEB, MAR, APR, MAY, JUN,
JUL, AUG, SEP, OCT, NOV, DEC } ;
name of new type list of all possible values of this new type
56
enum Type Declaration
enum MonthType { JAN, FEB, MAR, APR, MAY, JUN,
JUL, AUG, SEP, OCT, NOV, DEC } ;
the enum declaration creates a new programmer-defined type and lists all the possible values of that type--any valid C++ identifiers can be used as values
the listed values are ordered as listed. That is, JAN < FEB < MAR < APR , and so on
you must still declare variables of this type
57
Declaring enum Type Variables
enum MonthType { JAN, FEB, MAR, APR, MAY, JUN,
JUL, AUG, SEP, OCT, NOV, DEC } ;
MonthType thisMonth; // declares 2 variables
MonthType lastMonth; // of type MonthType
lastMonth = OCT ; // assigns values
thisMonth = NOV ; // to these variables...
lastMonth = thisMonth ;
thisMonth = DEC ;
58
Storage of enum Type Variables
enum MonthType { JAN, FEB, MAR, APR, MAY, JUN,
JUL, AUG, SEP, OCT, NOV, DEC } ;
stored as 0 stored as 1 stored as 2 stored as 3 etc.
stored as 11
59
Use Type Cast to Incrementenum Type Variables
enum MonthType { JAN, FEB, MAR, APR, MAY, JUN,
JUL, AUG, SEP, OCT, NOV, DEC } ;
MonthType thisMonth;
MonthType lastMonth;
lastMonth = OCT ;
thisMonth = NOV ;
lastMonth = thisMonth ;
thisMonth = thisMonth++ ; // COMPILE ERROR !
thisMonth = MonthType( thisMonth + 1) ; // uses type cast
60
More about enum Type
Enumeration type can be used in a Switch statement for the switch expression and the case labels.
Stream I/O ( using the insertion << and extraction >> operators ) is not defined for enumeration types. Instead, functions can be written for this purpose.
Comparison of enum type values is defined using the 6 relational operators ( < , <= , > , >= , == , != ).
An enum type can be the return type of a value-returning function in C++.
SOME EXAMPLES . . .
61
MonthType thisMonth;
switch ( thisMonth ) // using enum type switch expression
{
case JAN :
case FEB :
case MAR : cout << “Winter quarter” ;
break ;
case APR :
case MAY :
case JUN : cout << “Spring quarter” ;
break ;
case JUL :
case AUG :
case SEP : cout << “Summer quarter” ;
break ;
case OCT :
case NOV :
case DEC : cout << “Fall quarter” ;
}
62
Using enum type Control Variable with for Loop
enum MonthType { JAN, FEB, MAR, APR, MAY, JUN,
JUL, AUG, SEP, OCT, NOV, DEC } ;
void WriteOutName ( /* in */ MonthType ) ; // prototype.. .
MonthType month ;
for (month = JAN ; month <= DEC ; month = MonthType (month + 1 ) )
{ // requires use of type cast to increment
WriteOutName ( month ) ; // function call to perform output ...
}
63
void WriteOutName ( /* in */ MonthType month )// Prints out calendar name corresponding to month// Precondition: month is assigned// Postcondition: calendar name for month has been written out
{ switch ( month )
{
case JAN : cout << “ January ” ; break ;
case FEB : cout << “ February ” ; break ;
case MAR : cout << “ March ” ; break ;
case APR : cout << “ April ” ; break ;
case MAY : cout << “ May ” ; break ;
case JUN : cout << “ June ” ; break ;
case JUL : cout << “ July ” ; break ;
case AUG : cout << “ August ” ; break ;
case SEP : cout << “ September ” ; break ;
case OCT : cout << “ October ” ; break ;
case NOV : cout << “ November ” ; break ;
case DEC : cout << “ December ” ; break ;
}
}
64
enum SchoolType { PRE_SCHOOL, ELEM_SCHOOL, MIDDLE_SCHOOL, HIGH_SCHOOL, COLLEGE } ;
.
.
.
SchoolType GetSchoolData ( void )
// Obtains information from keyboard to determine school level// Postcondition: Function value == personal school level{
SchoolType schoolLevel ;
int age ;
int lastGrade ;
cout << “Enter age : “ ; // prompt for information
cin >> age ;
Function with enum type Return Value
65
if ( age < 6 )
schoolLevel = PRE_SCHOOL ;
else
{ cout << “Enter last grade completed in school : “ ;
cin >> lastGrade;
if ( lastGrade < 5 )
schoolLevel = ELEM_SCHOOL ;
else if ( lastGrade < 8 )
schoolLevel = MIDDLE_SCHOOL ;
else if ( lastGrade < 12 )
schoolLevel = HIGH_SCHOOL ;
else
schoolLevel = COLLEGE ;
}
return schoolLevel ; // return enum type value
}
66
Array with enum Index Type
DECLARATIONenum Department { WOMENS, MENS, CHILDRENS,
LINENS, HOUSEWARES, ELECTRONICS };
float salesAmt [ 6 ] ;
Department which;
USEfor ( which = WOMENS ; which <= ELECTRONICS ;
which = Department ( which + 1 ) )
cout << salesAmt [ which ] << endl;
67
float salesAmt[6];
salesAmt [ WOMENS ] ( i. e. salesAmt [ 0 ] )
salesAmt [ MENS] ( i. e. salesAmt [ 1 ] )
salesAmt [ CHILDRENS ] ( i. e. salesAmt [ 2 ] )
salesAmt [ LINENS ] ( i. e. salesAmt [ 3 ] )
salesAmt [ HOUSEWARES ] ( i. e. salesAmt [ 4 ] )
salesAmt [ ELECTRONICS ] ( i. e. salesAmt [ 5 ] )
68
Switch Statement
Is a selection control structure for multi-way branching.
SYNTAXswitch ( IntegralExpression )
{
case Constant1 :
Statement(s); // optional
case Constant2 :
Statement(s); // optional . . .
default : // optional
Statement(s); // optional
}
69
float weightInPounds = 165.8 ;char weightUnit ;
. . . // user enters letter for desired weightUnitswitch ( weightUnit ){
case ‘P’ :case ‘p’ :
cout << weightInPounds << “ pounds “ << endl ;break ;
case ‘O’ :case ‘o’ :
cout << 16.0 * weightInPounds << “ ounces “ << endl ;break ;
case ‘K’ :case ‘k’ :
cout << weightInPounds / 2.2 << “ kilos “ << endl ;break ;
case ‘G’ :case ‘g’ :
cout << 454.0 * weightInPounds << “ grams “ << endl ;break ;
default :cout << “That unit is not handled! “ << endl ;break ;
}
70
Switch Statement
the value of IntegralExpression (of char, short, int, long or enum type ) determines which branch is executed
case labels are constant ( possibly named ) integral expressions. Several case labels can precede a statement
71
Control in Switch Statement control branches to the statement following the case
label that matches the value of IntegralExpression. Control proceeds through all remaining statements, including the default, unless redirected with break
if no case label matches the value of IntegralExpression, control branches to the default label, if present--otherwise control passes to the statement following the entire switch statement
forgetting to use break can cause logical errors because after a branch is taken, control proceeds sequentially until either break or the end of the switch statement occurs