Define a class RecurringPatterns and define method in it which will print the following patter for n=4, after taking an integer argument n.

Question

Define a class RecurringPatterns and define method in it which will print the following patter for n=4, after taking an integer argument n.

                                     x

                                  x   x

                               x    x   x

                            x    x    x   x

                               x    x    x

                                  x     x

                                      x

Please explain the steps.

Answer 1

First of all you should think how you can derive your magic number (INPUT argument) n which 4 in your example out of the OUTPUT.

Output in console shows 4 inclined lines of x's.

 

In short, I suggest the RECURSIVE ALGORITHM to solve this problem.

Define a global variable 'time' and declare it as an integer and initialize it with 0; This variable controls the spaces between each pair of X.

Write down your 'main' and call your method as below:

 

public static void main(String[] args) {
    recurringPatterns(4); // the input argument varies from 0 to a desired integer.
}

 

----------

method'd bulk:

There are three important parts in your method:

1. The recursion termination for the recursive algorithm
2. drawing the upper-side of the output (diamond)
3. drawing the ower-side of the output

 

 

How to output upper-side line by line:

     X
   X X
  X X X
X X X X

 

Termination Condition in this algorithm is:

if (n == 0) {

   return;

}else{

   ....

}

// Now fill in the blank with the following piece of code:

// draw upper part of the output (diamond)
for (int i = 0; i < n - 1; i++) {
    System.out.print(' '); // left-end space
}

for (int i = 0; i < time; i++) {
    System.out.print('x');
    System.out.print(' '); // middle space
}

    System.out.println('x'); // right-end x
n--;
time++;

// At the time with the updated values of n and time your should be ready to RECALL the method:

recurringPatterns(n);

// Note that 'n' is subtracted by 1. and the value of variable 'time' is increased by 1.

// We are here because the algorithm satisfied the Recursion Termination. Thus, the value of n should be 0 by time.

// Reverse the whole operation above
// draw lower part of the output
n++;
time--;

if (time != 0) {
for (int i = 0; i < n; i++) {
    System.out.print(' ');
}

for (int i = 0; i < time - 1; i++) {
    System.out.print('x');
    System.out.print(' '); // middle space
}
System.out.println('x'); // right-end x

} else {
    return;
}

X X X
  X X
   X

Please note that this algorithm handles having no space after right-end X in each line.

Let me know if you need further description for more details.