programming-for-dummies

Using Queues 365
Counting and searching a stack
Because stacks can expand and shrink depending on the amount of data you
push on them, many programming languages give you commands to count
the total number of items currently stored in a stack.
In Visual Basic.NET, the command to count the number of items currently
stored in a stack is Count. Here’s an example:
Dim BlowMyStack as New Stack
Dim X as Object
BlowMyStack.Push (“My cat”)
BlowMyStack.Push (108.75)
BlowMyStack.Push (“Fat dog”)
X = BlowMyStack.Count
In this example, the Count command stores the number 3 in the X variable.
Visual Basic.NET also provides a Contains command, which tells you
whether a chunk of data is stored in a stack (but doesn’t tell you the location
of that data in the stack). To use the Contains command, you have to specify
the data you want to find like this:
Dim BlowMyStack as New Stack
Dim X, Y as Object
BlowMyStack.Push (“My cat”)
BlowMyStack.Push (108.75)
BlowMyStack.Push (“Fat dog”)
X = BlowMyStack.Contains(“Good dog”)
Y = BlowMyStack.Contains(“Fat dog”)
In this example, the first Contains command looks for the “Good dog”
string. Because this string isn’t stored in the stack, the Contains command
returns a False value, which it stored in the X variable.
Book III
Chapter 4
Stacks, Queues,
and Deques
The second Contains command looks for the “Fat dog” string. Because this
string is stored in the stack, this Contains command returns a True value,
which is stored in the Y variable.
The Contains command tells you whether a chunk of data is in a stack, but
it doesn’t tell you where in the stack that data might be.
Using Queues
Similar to a stack is another data structure — a queue.