Arrays

About This Presentation

Title:

Arrays

Description:

A array of five elements (type double) can be declared as: double s[5] ... There are five categories of hurricanes. Category 1 74 wind speed 96 mph ... – PowerPoint PPT presentation

Number of Views:43

Avg rating:3.0/5.0

Slides: 37

Provided by: adria9

Category:

more less

Transcript and Presenter's Notes

Title: Arrays

1
Arrays
2
Arrays

Suppose we have a set of 100 temperature
measurements that we want to analyze. It would be
tedious to write a program that has 100 different
variables corresponding to each temperature
measurement!
double temperature1, temperature2, temperature3

3
Arrays

Instead, we use a method that enables us to work
with a group of values with a single identifier
that is arrays.

4
Arrays

A array of five elements (type double) can be
declared as
double s5
This is a one dimensional array, which you can
visualize as a vector (row of values).
s0 0.5
s1 0.3
s2 -1.1
s3 4.2
s4 9.4

The array index is the offset from the first
element in the array
s0
s1
s2
s3
s4
s
Each element is a type double
s holds the address of the first element in the
array
5
Initialization

Initialization uses braces. The following two
array declarations and initializations are
equivalent.
double s5 0.5, 0.0, -0.1, 0.2, 0.15
double s 0.5, 0.0, -0.1, 0.2, 0.15
The following two array declarations and
initializations are equivalent.
double s5 0.0, 0.0, 0.0, 0.0, 0.0
double s5 0.0

6
Initialization and Display

Write a program that first creates an array that
has the values between 0 to 10 in steps of 0.5,
and second displays the contents of the array,
along with its offset location.

include ltiostreamgt
include ltiomanipgt
using namespace std
int main()
double x21
int i // this variable is used as the
current offset
// initialize the array with the values
for (i 0 i lt 21 i)
xi i0.5
cout ltlt setw(10) ltlt "Offset"
ltlt setw(10) ltlt "Value" ltlt endl
cout ltlt setw(10) ltlt "------"
ltlt setw(10) ltlt "-----" ltlt endl

8
Reverse Array

Write a program that first creates an array that
has the values between 0 to 10 in steps of 0.5,
and second displays the contents of the array,
along with its offset location, in reverse order.

include ltiostreamgt
include ltiomanipgt
using namespace std
int main()
double x21
int i // this variable is used as the
current offset
// initialize the array with the values
for (i 0 i lt 21 i)
xi i0.5
cout ltlt setw(10) ltlt "Offset"
ltlt setw(10) ltlt "Value" ltlt endl
cout ltlt setw(10) ltlt "------"
ltlt setw(10) ltlt "-----" ltlt endl

10
Display array

include ltiostreamgt
using namespace std
const int N 5
int main()
int xN 1,2,3,4,5
int i // this variable is used as the
current offset
for (i 0 i lt N i)
cout ltlt xi ltlt " "
cout ltlt endl
system("pause")
return 0

11
Falling off the end of the array

include ltiostreamgt
using namespace std
const int N 5
int main()
int xN 1,2,3,4,5
int i // this variable is used as the
current offset
for (i 0 i lt N i)
cout ltlt xi ltlt " "
cout ltlt endl
system("pause")
return 0

This should be i lt N. This means the loop will
execute for i 5. What will happen when it tries
to display x5?
What would happen instead of displaying x5, we
assigned a value to x5! What would happen then?
12
Static versus Dynamic arrays

In this course, we will only be considering
static arrays that is, the size of the array
will be constant.
There are dynamic arrays, where the size changes
when we allocate/deallocate memory to the array.
We will not be considering dynamic arrays in this
course.

13
Partially filled array

Write a program that accepts user inputs of
integers, which are placed in an array. The
program continues to accept user inputs until 10
inputs are received, or until the user enters -1.
When the program is finished receiving inputs,
the program should then display the array
contents.

include ltiostreamgt
using namespace std
const int NMAX 10
int main()
int xNMAX
int n 0, i
while (n lt NMAX)
cout ltlt "Enter an input (-1 to quit) "
cin gtgt xn
if (xn -1)
break

15
Functions and Arrays

double s5
Recall that s0 is the value of the first
element in the array and the s is the memory
address of the array.
Arrays used in function are inherently pass by
reference because we are passing the address of
the array into a function.

16
Reverse and Display

Write a function that displays the contents of an
array.
Write a function that reverses the contents of an
array.
Write a program that has an array of elements 1
to 20, displays the array, reverses the array,
and displays the array again.

include ltiostreamgt
using namespace std
const int N 19
void display_array(int y, int n)
void reverse_array(int y, int n)
int main()
int xN, i
for (i 0 i lt N i)
xi i 1
display_array(x, N)
reverse_array(x, N)

void display_array(int y, int n)
int i
for (i 0 i lt n i)
cout ltlt yi ltlt " "
cout ltlt endl
return
void reverse_array(int y, int n)
int tempN, i
for (i 0 i lt n i)
tempi yi

19
Functions and Arrays

In the many cases, functions that include arrays
will often have two input parameters the array
and the number of valid inputs.

20
Max value in array

Write a function that accepts user inputs of
integers, which are placed in an array. The
function continues to accept user inputs until
100 inputs are received, or until the user enters
-1. The function should return the number of user
inputs.
When a function that returns the maximum value in
an array.
Write a program that accepts user inputs until a
-1 is entered or until 100 inputs are received.
The program should then display the user inputs
and the maximum value.

include ltiostreamgt
using namespace std
const int NMAX 100
void display_array(int x, int n)
int fill_array(int x, int nmax)
int max_in_array(int x, int n)
int main()
int xNMAX, n
n fill_array(x, nmax)
display_array(x,n)
cout ltlt "The maximum value is "
ltlt max_in_array(x,n) ltlt endl

void display_array(int x, int n)
int i
for (i 0 i lt n i)
cout ltlt xi ltlt " "
cout ltlt endl
return
int fill_array(int x, int nmax)
int i 0
while (i lt nmax)
cout ltlt "Enter an integer -1 to stop) "
cin gtgt xi

int max_in_array(int x, int n)
int i, maxval x0
for (i 1 i lt n i)
if (xi gt maxval)
maxval xi
return maxval

24
Hurricane

There are five categories of hurricanes
Category 1 74 ? wind speed lt 96 mph
Category 2 96 ? wind speed lt 111 mph
Category 3 111 ? wind speed lt 131 mph
Category 4 131 ? wind speed lt 155 mph
Category 5 155 mph ? wind speed
Suppose we have a data file storm.txt that
contains a numerical identification for each
storm within a year and the peak wind speed.
Write a program that outputs a table that
contains the identification number, peak wind,
and category of each hurricane. Storms that are
not a hurricane are simply ignored. Note that
there are at most 100 hurricanes a year.

include ltiostreamgt
include ltfstreamgt
include ltiomanipgt
using namespace std
const int NMAX 100
int category(double wind_speed)
int main()
int idNMAX, storm_categoryNMAX, n 0, i
double peak_windNMAX
ifstream fin
fin.open("storm.txt")
while (!fin.eof() n lt NMAX)
fin gtgt idn gtgt peak_windn

cout ltlt setw(20) ltlt "Identification"
ltlt setw(20) ltlt "Peak Wind"
ltlt setw(20) ltlt "Category" ltlt endl
cout ltlt setw(20) ltlt "--------------"
ltlt setw(20) ltlt "---------"
ltlt setw(20) ltlt "--------" ltlt endl
for (i 0 i lt n i)
cout ltlt setw(20) ltlt idi
ltlt setw(20) ltlt peak_windi
ltlt setw(20) ltlt storm_categoryi ltlt
endl
cout ltlt endl ltlt "There were " ltlt n
ltlt " storms that were hurricanes" ltlt
endl
system("pause")
return 0

/------------------------------------------------
-------------------------
int category(double wind_speed)
Author Adrian Chan
Student ID 100123456
This function determines the hurriance category
of a storm.
Category 1 74 lt wind speed lt 96 mph
Category 2 96 lt wind speed lt 111 mph
Category 3 111 lt wind speed lt 131 mph
Category 4 131 lt wind speed lt 155 mph
Category 5 155 mph lt wind speed
Inputs
wind_speed the peak wind speed of the storm
Outputs
double category number

int category(double wind_speed)
if (wind_speed gt 155.0)
return 5
else if (wind_speed gt 131.0)
return 4
else if (wind_speed gt 111.0)
return 3
else if (wind_speed gt 96.0)
return 2
else if (wind_speed gt 74.0)
return 1
return 0

29
Hurricane

Did you need to use an array for this
question?!?!?!?!

include ltiostreamgt
include ltfstreamgt
include ltiomanipgt
using namespace std
int category(double wind_speed)
int main()
int id, storm_category, n 0, i
double peak_wind
ifstream fin
cout ltlt setw(20) ltlt "Identification"
ltlt setw(20) ltlt "Peak Wind"
ltlt setw(20) ltlt "Category" ltlt endl
cout ltlt setw(20) ltlt "--------------"
ltlt setw(20) ltlt "---------"

/------------------------------------------------
-------------------------
int category(double wind_speed)
Author Adrian Chan
Student ID 100123456
This function determines the hurriance category
of a storm.
Category 1 74 lt wind speed lt 96 mph
Category 2 96 lt wind speed lt 111 mph
Category 3 111 lt wind speed lt 131 mph
Category 4 131 lt wind speed lt 155 mph
Category 5 155 mph lt wind speed
Inputs
wind_speed the peak wind speed of the storm
Outputs
double category number

32
Hurricane

It would be better to use arrays if
You needed to display the number of storms that
were hurricanes first
You were going to put an asterisk next to the row
that had the highest wind speed

include ltiostreamgt
include ltfstreamgt
include ltiomanipgt
using namespace std
const int NMAX 100
int category(double wind_speed)
int main()
int idNMAX, storm_categoryNMAX, n 0, i,
index_max 0
double peak_windNMAX
ifstream fin
fin.open("storm.txt")
while (!fin.eof() n lt NMAX)
fin gtgt idn gtgt peak_windn

This is not the maximum peak wind but rather than
offset index where the maximum peak wind is
located in the array. Initialize it to the first
element in the array
See how the index_max is updated
34