Study Guide
Chapter 9 Arrays
-
University:
Kentucky State University -
Course:
COS 232| Programming I Academic year:
2020
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Views:
28
Pages:
35
Author:
Tyshawn Shaffer
Chapter 9: Arrays Data Types
• A data type is called simple if variables of that
type can store only one value at a time
• A structured data type is one in which each
data item is a collection of other data items
2 Arrays
• Array: a collection of a fixed number of
components wherein all of the components
have the same data type
• In a one-dimensional array, the components
are arranged in a list form
• Syntax for declaring a one-dimensional array:
intExp evaluates to a positive integer
3 Arrays (continued)
• Example:
int num[5];
4 Accessing Array Components
• General syntax:
where indexExp, called an index, is any expression
whose value is a nonnegative integer
• Index value specifies the position of the
component in the array
• [] is the array subscripting operator
• The array index always starts at 0
5 Accessing Array Components
(continued)
6 Accessing Array Components
(continued)
7 Accessing Array Components
(continued)
8 Accessing Array Components
(continued)
9 Processing One-Dimensional Arrays
• Some basic operations performed on a onedimensional array are:
− Initializing
− Inputting data
− Outputting data stored in an array
− Finding the largest and/or smallest element
• Each operation requires ability to step through
the elements of the array
• Easily accomplished by a loop
10 Processing One-Dimensional Arrays
(continued)
• Consider the declaration
int list[100];
int i;
//array of size 100
• Using for loops to access array elements:
for (i = 0; i < 100; i++) //Line 1
//process list[i]
//Line 2
• Example:
for (i = 0; i < 100; i++) //Line 1
cin >> list[i];
//Line 2
11 Array Index Out of Bounds
• If we have the statements:
double num[10];
int i;
• The component num[i] is valid if i = 0, 1, 2,
3, 4, 5, 6, 7, 8, or 9
• The index of an array is in bounds if the index
>=0 and the index <= ARRAY_SIZE-1
− Otherwise, we say the index is out of bounds
• In C++, there is no guard against indices that
are out of bounds
13 Array Initialization During
Declaration
• Arrays can be initialized during declaration
− In this case, it is not necessary to specify the size
of the array
• Size determined by the number of initial values in the
braces
• Example:
double sales[] = {12.25, 32.50, 16.90, 23, 45.68};
14 Partial Initialization of Arrays
During Declaration
• The statement:
int list[10] = {0};
declares list to be an array of 10 components
and initializes all of them to zero
• The statement:
int list[10] = {8, 5, 12};
declares list to be an array of 10 components,
initializes list[0] to 8, list[1] to 5,
list[2] to 12 and all other components are
initialized to 0
15 Partial Initialization of Arrays
During Declaration (continued)
• The statement:
int list[] = {5, 6, 3};
declares list to be an array of 3 components
and initializes list[0] to 5, list[1] to 6, and
list[2] to 3
• The statement:
int list[25]= {4, 7};
declares an array of 25 components; initializes
list[0] to 4 and list[1] to 7; all other
components are initialized to 0
16 Some Restrictions on Array
Processing
• Consider the following statements:
• C++ does not allow aggregate operations on
an array:
• Solution:
17 Some Restrictions on Array
Processing (continued)
• The following is illegal too:
• Solution:
• The following statements are legal, but do not
give the desired results:
18 Two-Dimensional Arrays
• Two-dimensional array: collection of a fixed
number of components (of the same type)
arranged in two dimensions
− Sometimes called matrices or tables
• Declaration syntax:
where intexp1 and intexp2 are expressions
yielding positive integer values, and specify the
number of rows and the number of columns,
respectively, in the array
19 Two-Dimensional Arrays
(continued)
20 Accessing Array Components
• Syntax:
where indexexp1 and indexexp2 are
expressions yielding nonnegative integer values,
and specify the row and column position
21 Accessing Array Components
(continued)
22 Two-Dimensional Array
Initialization During Declaration
• Two-dimensional arrays can be initialized
when they are declared:
− Elements of each row are enclosed within
braces and separated by commas
− All rows are enclosed within braces
− For number arrays, if all components of a row
aren’t specified, unspecified ones are set to 0
23 Processing Two-Dimensional
Arrays
• Ways to process a two-dimensional array:
− Process the entire array
− Process a particular row of the array, called
row processing
− Process a particular column of the array,
called column processing
• Each row and each column of a twodimensional array is a one-dimensional array
− To process, use algorithms similar to
processing one-dimensional arrays
24 Processing Two-Dimensional
Arrays (continued)
25 Initialization
• To initialize row number 4 (i.e., fifth row) to 0
• To initialize the entire matrix to 0:
26 Print
• To output the components of matrix:
27 Input
• To input data into each component of
matrix:
28 Sum by Row
• To find the sum of row number 4 of matrix:
• To find the sum of each individual row:
29 Sum by Column
• To find the sum of each individual column:
30 Largest Element in Each Row and
Each Column
31 Summary
• Array: structured data type with a fixed
number of components of the same type
− Components are accessed using their relative
positions in the array
• Elements of a one-dimensional array are
arranged in the form of a list
• An array index can be any expression that
evaluates to a nonnegative integer
− Must always be less than the size of the array
32 Summary (continued)
• The base address of an array is the address
of the first array component
• When passing an array as an actual
parameter, you use only its name
− Passed by reference only
• A function cannot return a value of the type
array
33 Summary (continued)
• Parallel arrays are used to hold related
information
• In a two-dimensional array, the elements are
arranged in a table form
34 Summary
• To access an element of a two-dimensional
array, you need a pair of indices:
− One for the row position
− One for the column position
• In row processing, a two-dimensional array is
processed one row at a time
• In column processing, a two-dimensional
array is processed one column at a time
35
Chapter 9 Arrays
of 35
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