Arrays

1
Arrays
2
Overview

• Arrays and their properties
• Creating arrays
• Accessing array elements
• Modifying array elements
• Loops and arrays
• Initialization
• Searching

3
Arrays and Their Properties

• Hold several values of the same type
  (homogeneous)
• Based on a slot number (the index number)
• Instant access
• Linear (one after the other)
• Static once their size is set, its set

4
What arrays look like

• Things to notice
• There are 7 slots, with index numbers 0 6
• The name of the array is myArray
• Easy to be off by one

0
1
2
3
4
5
6
myArray
5
Creating Arrays

• ltdata typegt ltnamegt new ltdata typegt ltsizegt
• new brings complex variables to life in C
• Notice that we can create an array of any data
  type, just by changing the data type!

6
Examples

• An array of shorts
• short someArray new short50
• An array of floats
• float myArray new float25
• An array of booleans
• bool list new bool65
• An array of chars
• char characters new char255

7
Initializing Arrays with Values

• ltdata typegt ltnamegt new ltdata typegt ltsizegt
  VALUES
• Or
• ltdata typegt ltnamegt VALUES

8
Modifying an Array

• You must specify which slot you are putting
  information in
• Example
• int myArray new int50
• myArray3 12
• This wont work
• int myArray new int50
• myArray 12
• Data type on the left of is an array
• Data type on right of is an int

0
1
2
3
4
49

12
9
Accessing Information

• Copying information out of a particular slot
• Example
• int clientAge
• clientAge myArray4
• This copies information from the fifth slot (slot
  four) into the variable clientAge

10
Initializing Arrays(large arrays)

• For most arrays, you will use a loop to
  initialize
• Problem create an array of 50 bytes and fill
  each slot with the number 42
• Solution
• byte myList new byte50
• for (int counter0 counter lt 50 counter)
• myListcounter 42

11
Line by Line(a smaller example)

• byte myList new byte5
• for (int counter 0 counter lt 5 counter)
• myList counter 42

12
Line by Line

• byte myList new byte5
• for (int counter 0 counter lt 5 counter)
• myList counter 42

0
1
2
3
4
0
0
0
0
0
13
Line by Line

• byte myList new byte5
• for (int counter 0 counter lt 5 counter)
• myList counter 42

counter
0
0
1
2
3
4
0
0
0
0
0
14
Line by Line

• byte myList new byte5
• for (int counter 0 counter lt 5 counter)
• myList counter 42

counter
0
0
1
2
3
4
0
0
0
0
0
15
Line by Line

• byte myList new byte5
• for (int counter 0 counter lt 5 counter)
• myList counter 42

counter
0
0
1
2
3
4
0
0
0
0
0
16
Line by Line

• byte myList new byte5
• for (int counter 0 counter lt 5 counter)
• myList counter 42

counter
0
0
1
2
3
4
42
0
0
0
0
17
Line by Line

• byte myList new byte5
• for (int counter 0 counter lt 5 counter)
• myList counter 42

counter
1
0
1
2
3
4
42
0
0
0
0
18
Line by Line

• byte myList new byte5
• for (int counter 0 counter lt 5 counter)
• myList counter 42

counter
1
0
1
2
3
4
42
0
0
0
0
19
Line by Line

• byte myList new byte5
• for (int counter 0 counter lt 5 counter)
• myList counter 42

counter
1
0
1
2
3
4
42
0
0
0
0
20
Line by Line

• byte myList new byte5
• for (int counter 0 counter lt 5 counter)
• myList counter 42

counter
1
0
1
2
3
4
42
42
0
0
0
21
Line by Line

• byte myList new byte5
• for (int counter 0 counter lt 5 counter)
• myList counter 42

counter
2
0
1
2
3
4
42
42
0
0
0
22
Line by Line

• byte myList new byte5
• for (int counter 0 counter lt 5 counter)
• myList counter 42

counter
2
0
1
2
3
4
42
42
0
0
0
23
Line by Line

• byte myList new byte5
• for (int counter 0 counter lt 5 counter)
• myList counter 42

counter
2
0
1
2
3
4
42
42
0
0
0
24
Line by Line

• byte myList new byte5
• for (int counter 0 counter lt 5 counter)
• myList counter 42

counter
2
0
1
2
3
4
42
42
42
0
0
25
Line by Line

• byte myList new byte5
• for (int counter 0 counter lt 5 counter)
• myList counter 42

counter
3
0
1
2
3
4
42
42
42
0
0
26
Line by Line

• byte myList new byte5
• for (int counter 0 counter lt 5 counter)
• myList counter 42

counter
3
0
1
2
3
4
42
42
42
0
0
27
Line by Line

• byte myList new byte5
• for (int counter 0 counter lt 5 counter)
• myList counter 42

counter
3
0
1
2
3
4
42
42
42
0
0
28
Line by Line

• byte myList new byte5
• for (int counter 0 counter lt 5 counter)
• myList counter 42

counter
3
0
1
2
3
4
42
42
42
42
0
29
Line by Line

• byte myList new byte5
• for (int counter 0 counter lt 5 counter)
• myList counter 42

counter
4
0
1
2
3
4
42
42
42
42
0
30
Line by Line

• byte myList new byte5
• for (int counter 0 counter lt 5 counter)
• myList counter 42

counter
4
0
1
2
3
4
42
42
42
42
0
31
Line by Line

• byte myList new byte5
• for (int counter 0 counter lt 5 counter)
• myList counter 42

counter
4
0
1
2
3
4
42
42
42
42
0
32
Line by Line

• byte myList new byte5
• for (int counter 0 counter lt 5 counter)
• myList counter 42

counter
4
0
1
2
3
4
42
42
42
42
42
33
Line by Line

• byte myList new byte5
• for (int counter 0 counter lt 5 counter)
• myList counter 42

counter
5
0
1
2
3
4
42
42
42
42
42
34
Line by Line
false

• byte myList new byte5
• for (int counter 0 counter lt 5 counter)
• myList counter 42

counter
5
0
1
2
3
4
42
42
42
42
42
35
Finding the Smallest Element

• If you were given an array of numbers, how would
  YOU do it?
• Computers can only compare two at a time
• Go through entire list
• Keep track of smallest so far
• Lets assume
• We have an array of 5 integers
• The array contains random unknown numbers
• The name of the array is called randomArray

36
Another Trace

• int smallestSoFar
• smallestSoFar randomArray0
• for (int counter 1 counter lt 5 counter)
• if (smallestSoFar gt randomArraycounter)
• smallestSoFar randomArraycounter
• //if
• //for

0
1
2
3
4
smallestSoFar
42
17
42
-8
4
37
Another Trace

• int smallestSoFar
• smallestSoFar randomArray0
• for (int counter 1 counter lt 5 counter)
• if (smallestSoFar gt randomArraycounter)
• smallestSoFar randomArraycounter
• //if
• //for

0
1
2
3
4
smallestSoFar
42
17
42
-8
4
38
Another Trace

• int smallestSoFar
• smallestSoFar randomArray0
• for (int counter 1 counter lt 5 counter)
• if (smallestSoFar gt randomArraycounter)
• smallestSoFar randomArraycounter
• //if
• //for

0
1
2
3
4
smallestSoFar
42
42
17
42
-8
4
39
Another Trace

• int smallestSoFar
• smallestSoFar randomArray0
• for (int counter 1 counter lt 5 counter)
• if (smallestSoFar gt randomArraycounter)
• smallestSoFar randomArraycounter
• //if
• //for

counter
1
0
1
2
3
4
smallestSoFar
42
42
17
42
-8
4
40
Another Trace

• int smallestSoFar
• smallestSoFar randomArray0
• for (int counter 1 counter lt 5 counter)
• if (smallestSoFar gt randomArraycounter)
• smallestSoFar randomArraycounter
• //if
• //for

counter
1
0
1
2
3
4
smallestSoFar
42
42
17
42
-8
4
41
Another Trace

• int smallestSoFar
• smallestSoFar randomArray0
• for (int counter 1 counter lt 5 counter)
• if (smallestSoFar gt randomArraycounter)
• smallestSoFar randomArraycounter
• //if
• //for

Is 42 gt 17?
counter
1
0
1
2
3
4
smallestSoFar
42
42
17
42
-8
4
42
Another Trace

• int smallestSoFar
• smallestSoFar randomArray0
• for (int counter 1 counter lt 5 counter)
• if (smallestSoFar gt randomArraycounter)
• smallestSoFar randomArraycounter
• //if
• //for

counter
1
0
1
2
3
4
smallestSoFar
17
42
17
42
-8
4
43
Another Trace

• int smallestSoFar
• smallestSoFar randomArray0
• for (int counter 1 counter lt 5 counter)
• if (smallestSoFar gt randomArraycounter)
• smallestSoFar randomArraycounter
• //if
• //for

counter
1
0
1
2
3
4
smallestSoFar
17
42
17
42
-8
4
44
Another Trace

• int smallestSoFar
• smallestSoFar randomArray0
• for (int counter 1 counter lt 5 counter)
• if (smallestSoFar gt randomArraycounter)
• smallestSoFar randomArraycounter
• //if
• //for

counter
2
0
1
2
3
4
smallestSoFar
17
42
17
42
-8
4
45
Another Trace

• int smallestSoFar
• smallestSoFar randomArray0
• for (int counter 1 counter lt 5 counter)
• if (smallestSoFar gt randomArraycounter)
• smallestSoFar randomArraycounter
• //if
• //for

counter
2
0
1
2
3
4
smallestSoFar
17
42
17
42
-8
4
46
Another Trace

• int smallestSoFar
• smallestSoFar randomArray0
• for (int counter 1 counter lt 5 counter)
• if (smallestSoFar gt randomArraycounter)
• smallestSoFar randomArraycounter
• //if
• //for

Is 17 gt 42?
counter
2
0
1
2
3
4
smallestSoFar
17
42
17
42
-8
4
47
Another Trace

• int smallestSoFar
• smallestSoFar randomArray0
• for (int counter 1 counter lt 5 counter)
• if (smallestSoFar gt randomArraycounter)
• smallestSoFar randomArraycounter
• //if
• //for

counter
2
0
1
2
3
4
smallestSoFar
17
42
17
42
-8
4
48
Another Trace

• int smallestSoFar
• smallestSoFar randomArray0
• for (int counter 1 counter lt 5 counter)
• if (smallestSoFar gt randomArraycounter)
• smallestSoFar randomArraycounter
• //if
• //for

counter
3
0
1
2
3
4
smallestSoFar
17
42
17
42
-8
4
49
Another Trace

• int smallestSoFar
• smallestSoFar randomArray0
• for (int counter 1 counter lt 5 counter)
• if (smallestSoFar gt randomArraycounter)
• smallestSoFar randomArraycounter
• //if
• //for

counter
3
0
1
2
3
4
smallestSoFar
17
42
17
42
-8
4
50
Another Trace

• int smallestSoFar
• smallestSoFar randomArray0
• for (int counter 1 counter lt 5 counter)
• if (smallestSoFar gt randomArraycounter)
• smallestSoFar randomArraycounter
• //if
• //for

Is 17 gt -8?
counter
3
0
1
2
3
4
smallestSoFar
17
42
17
42
-8
4
51
Another Trace

• int smallestSoFar
• smallestSoFar randomArray0
• for (int counter 1 counter lt 5 counter)
• if (smallestSoFar gt randomArraycounter)
• smallestSoFar randomArraycounter
• //if
• //for

counter
3
0
1
2
3
4
smallestSoFar
-8
42
17
42
-8
4
52
Another Trace

• int smallestSoFar
• smallestSoFar randomArray0
• for (int counter 1 counter lt 5 counter)
• if (smallestSoFar gt randomArraycounter)
• smallestSoFar randomArraycounter
• //if
• //for

counter
3
0
1
2
3
4
smallestSoFar
-8
42
17
42
-8
4
53
Another Trace

• int smallestSoFar
• smallestSoFar randomArray0
• for (int counter 1 counter lt 5 counter)
• if (smallestSoFar gt randomArraycounter)
• smallestSoFar randomArraycounter
• //if
• //for

counter
4
0
1
2
3
4
smallestSoFar
-8
42
17
42
-8
4
54
Another Trace

• int smallestSoFar
• smallestSoFar randomArray0
• for (int counter 1 counter lt 5 counter)
• if (smallestSoFar gt randomArraycounter)
• smallestSoFar randomArraycounter
• //if
• //for

counter
4
0
1
2
3
4
smallestSoFar
-8
42
17
42
-8
4
55
Another Trace

• int smallestSoFar
• smallestSoFar randomArray0
• for (int counter 1 counter lt 5 counter)
• if (smallestSoFar gt randomArraycounter)
• smallestSoFar randomArraycounter
• //if
• //for

Is -8 gt 4?
counter
4
0
1
2
3
4
smallestSoFar
-8
42
17
42
-8
4
56
Another Trace

• int smallestSoFar
• smallestSoFar randomArray0
• for (int counter 1 counter lt 5 counter)
• if (smallestSoFar gt randomArraycounter)
• smallestSoFar randomArraycounter
• //if
• //for

counter
4
0
1
2
3
4
smallestSoFar
-8
42
17
42
-8
4
57
Another Trace

• int smallestSoFar
• smallestSoFar randomArray0
• for (int counter 1 counter lt 5 counter)
• if (smallestSoFar gt randomArraycounter)
• smallestSoFar randomArraycounter
• //if
• //for

counter
5
0
1
2
3
4
smallestSoFar
-8
42
17
42
-8
4
58
Another Trace

• int smallestSoFar
• smallestSoFar randomArray0
• for (int counter 1 counter lt 5 counter)
• if (smallestSoFar gt randomArraycounter)
• smallestSoFar randomArraycounter
• //if
• //for

counter
5
0
1
2
3
4
smallestSoFar
-8
42
17
42
-8
4
59
Another Trace

• int smallestSoFar
• smallestSoFar randomArray0
• for (int counter 1 counter lt 5 counter)
• if (smallestSoFar gt randomArraycounter)
• smallestSoFar randomArraycounter
• //if
• //for

counter
5
0
1
2
3
4
smallestSoFar
-8
42
17
42
-8
4
60
Summary

• Arrays hold values that are all the same type
• Arrays are static in size
• Creating arrays always follows a format
• You can create an array of any type
• To initialize or search arrays, youll almost
  always use a loop