DEPTH-FIRST SEARCHING USING RECURSION:
PROGRAMMING EXERCISES
1. Create a NumDigits application that prompts the user for an
integer and then outputs the number of digits in that number. So,
for example, the number 542 would return 3 because there are
three digits in the number 542. The number 72345 would return 5
because there are five digits in the number 72345. You will need
to include a recursive method called numDigits() that returns the
number of digits in any given number.
HINT: The number of digits in a number (n) is always one more than the number of
digits in n/10.
Your program output should look something like this:
Please enter an integer:
5234
The number 5234 contains 4 digits!
Save the project as NumDigits in your UNIT 4 folder.
2. Create an AntColonies application so that it reads slides that are digitized to report colour. For
example, a slide file could look like this:
6
8
00550000
00050000
00005500
01200000
01111000
00000030
The digits 1 through 9 represent various colours. The digit 0 represents no colony.
When the program launches, the user will need to click the OPEN button to open a text file that
contains the data.
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Once the file has been selected, the data from the file should be outputted in the JTextArea on the
right.
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When the user clicks REPORT, the program should use a depth-first searching algorithm to
determine and display a listing of the size, location, and colour value of each ant colony on the slide.
An ant colony is defined as a connected (horizontally or vertically) sequence of cells holding the same
colour value.
For the above slide, the application should output the following report:
Save the project as Ant Colonies in your UNIT 4 folder.
3. Create a MazeRunner application that finds the starting
point of a maze (labeled S) and finds a path to the goal
(labeled G). The maze must be read from a text file and will
be defined as follows:
‘X’
‘ ’
‘S’
‘G’
represents
represents
represents
represents
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walls
paths
the starting point
the goal
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So the text file would look something like this:
8
10
XXXXXXXXXX
XS
X
XX XXX XXX
XX
X
X
XXXX X X X
X
X XXX
X XXXX GX
XXXXXXXXXX
The first line of the text files indicates how many rows, the second line indicates how many columns
and the rest of the file is the maze itself.
When the program starts the user will need to click the OPEN button to select a text file using a
JFileChooser object:
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Once the file has been read, the maze should be outputted to the JTextArea on the left:
When the user clicks the SOLVE button, the program must trace the correct path to get to the goal
using a depth-first searching algorithm. You will need to trace the path taken by inserting a ‘.’ Once
the maze is solved and the goal is reached, you will need to output the solution to the JTextArea on
the right. So the solution to the above maze would look something like this:
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The pseudocode for the algorithm would look something like this:
public boolean solveMaze(int row, int col) {
If the space above, below, to the left and to the right of your
current position equals ‘G’
Insert a ‘.’ at the current position
Output the path taken
Return true
If your current position does not equal ‘S’
Insert a ‘.’ at the current position
If the position to the right of your current position is ‘ ’ and
the maze is not solved
Call the solveMaze method and pass it the position to the
right of your current position
If the position below your current position is ‘ ’ and the maze
is not solved
Call the solveMaze method and pass it the position below your
current position
If the position to the left of your current position is ‘ ’ and
the maze is not solved
Call the solveMaze method and pass it the position to the left
of your current position
If the position above your current position is ‘’ and the maze is
not solved
Call the solveMaze method and pass it the position above your
current position
If solved equals false
Insert a ‘ ’ at your current position
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}
Save the project as Maze Runner in your UNIT 4 folder.
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