Transcript Exam Review (ppt)

Computer Science II
Exam I Review
Monday, February 6, 2006
Material Coverage - Lectures
Lecture Date
2
Coverage
Intro &
1/17
Background
1/20 Background II
3
1/24 Strings
Chap 1,2
4
1/27 Vectors
Chap 3
5
1/31 C++ Classes I
Chap 4.2-4.4, Chap 9
1
6
2/3
C++ Classes II
Reading
K&M: Chap 0
Malik: see Lec Notes
Chap 0
Chap 4.2-4.4, Chap 9
Material Coverage Lab/HW Date
Lab 1
Lab 2
Lab 3
HW 1
HW 2
1/18
Labs &
HW
Coverage
Getting Started
Strings, Files, and
1/25
Command Line Arguments
C++ Classes
2/1
Due Getting Started
1/26
Due Moire Strings
2/2
Background Review
#include <iostream> // asks compiler for parts of std lib
int main( )
{
std::cout << “Hello, world!” << std::endl;
return 0;
}
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Know basic syntax
comments
 included files (why?)
 main is necessary for all programs
 expressions (Chap 2 of Malik book)
 variables, objects, types, constants
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Statement
single statement ending with ;
 structured statement (i.e. else if)
 compound statement delimited by
{…}
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Review statements, expressions, and
assignments
Arrays
fixed consecutive sequence of objects
all of the same type
 indexing starts at 0
 are a fixed size
 programmer’s responsibility to
prevent overflow
 constant arrays are similar to
constant variables – once initialized
they cannot be altered
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Functions and Arguments
Why use them?
 each has parameters and a return
type (including main!)
 order of parameters matters
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More Background Review
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Loop syntax for:
for loops
 while loops
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Loop invariant
logical assertion that is true at start of
each iteration of a loop
 stated as comment helps analyzing code
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switch statements
 If and else statements
 &&, ||, %, and other operators
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Background Review II
What is the difference between a
function prototype (declaration) and
definition?
 What is one way to return multiple
results from a function?
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Parameters to Functions
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Value parameter
local variable in function
 initial value is copy of argument value
 changes in function do not affect
corresponding argument in calling
function
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Reference parameter
alias for corresponding argument (not a
new variable)
 changes do affect corresponding
variables in calling function
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Arrays are tricky
Changes made to an array are
permanent, even if passed as value
parameters
 Why?
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Pass by value the memory location of
the base address of the array
Scope
of an identifier (name) is the part of
the program in which it has meaning
 { } establishes a new scope
 scopes may be nested
 identifiers may be reused as long as
they are in different scopes
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those with same name in inner scope
hide those in outer scope
:: establishes scope as well
Order Notation
Can compare why one algorithm is
better than another (usually using
worst case analysis)
 O(1)
 O(log n)
 O(n)
 O(n log n)
 O(n2)
 O(nk)
 O(2n)
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Strings
object type defined in std lib to
contain sequence of characters
 like all types, string type defines an
interface
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construction (initialization)
 operations
 functions (methods)
 other types
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More about strings
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Constructing string objects
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By default (create an empty string)
 string
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With a specified number of instances of
a single character
 string
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name;
stars(10, ‘*’);
From another string
 string
sentence = “I see stars ” + stars;
 string name(“Bettina”);
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L-value vs. R-value
Some member functions
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size()
length()
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size_type vs. unsigned int vs. int
+ operator concatenates two strings to
create a third
= assignment operation overwrites current
contents of string
strings behave like arrays when using []
operator
Vector
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Ideal for storage of items when you don’t
know how many values there will be in
advance
std lib container class
acts like a dynamically-size 1D array
holds objects of any type (must all be same
type)
starts empty unless otherwise specified
no limit on size
can use subscripting [] operator
no automatic checking of [] bounds
Templated Container Class
Vectors are an example
 <> are used to specify type of object
(template type) to be stored in vector
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vector<int> grades;
 vector<string> names;
 vector<float> temperatures;
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Some member functions
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push_back()
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O(1) on average
size()
 begin()
 end()
 [] operator (like with arrays)
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More about vectors
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Constructing vectors
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By default an empty vector
 vector<int>
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a;
With a specified number of instances of
a single object
 vector<double>
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With a specified number of instances
with no initial value
 vector<int>
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b(100, 3.14);
c(100);
From another vector (of same type!)
 vector<int>
d(b);
Sort
std lib function that deals with
container classes
 Sorts values from least to greatest if
no sorting function supplied
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sort(a.begin(), a.end());
 uses < operator on objects in vector
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Can specify your own comparison
function
sort(a.begin(), a.end(), IsEarlierThan);
 sort(a.begin(), a.end(), IsLaterThan);
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Vectors and Strings as Parameters
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Options:
pass by reference
 pass by value (expensive!)
 pass by constant reference
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Note: This is unlike arrays which are
never pass by value
Classes
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Defining a new type
Structure of memory within each class
object
Set of operations defined
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C++ classes consist of:
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collection of member variables (private)
collection of member functions (public)
public: can be accessed directly from
outside the class
private: can only be accessed indirectly
through public member functions
Classes Continued
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Each object of a class created has its own
distinct member variables
Call member functions using dot notation
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tomorrow.print();
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main.cpp
.cpp file for member function definitions
(implementation file)
.h file for class declaration (header file)
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include .h file in the two .cpp files above
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More on classes
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class scope ::
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member functions and variables are
accessible without name of object
constructors
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special functions that initialize values of
member variables
 only
called once per object
 default constructor has no arguments
 multiple allowed
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copy constructor automatically created
Member functions
Defined within class scope
 Same as before but modify object’s
member variables
 Can call member functions without
using object name
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Functions which are not members of
the class must use public member
functions wrt an object of that class
Constant Member Functions
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Member functions that do not change
the member variables should be
declared as this
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bool Date::isEqual(const Date &date2) const;
const must appear in both class declaration
(.h) and member function definition (.cpp)
const objects can only use const member
functions
Struct
What is it?
 Class where default protection is
public, not private
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Non-member operators
not declared/defined in class scope
but the arguments to the function are
class objects
 Examples:
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operator<
 operator+
 IsEarlierThan
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Exam 1
Tomorrow, Tuesday February 7
 10 – 11:50am
 West Hall Auditorium
 Closed book and closed notes
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except for 1 sheet of 8.5 x 11 paper
Bring your RPI ID!!
Questions?