In my previous tutorial Solving Programming Problems, I walked you threw the process of solving a generic programming problem. We made a method that printed out a tree structure in the console.

In this tutorial, I’ll walk through the process of finding bugs in the code and talk about how we can fix those bugs. I think this topic may be the hardest to teach. I hope the video and the code that follows can help you better grasp how to solve most any programming problem.

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**Code From the Video**

**Solving Programming Problems 2 : Heap2.java**

import java.util.Arrays; public class Heap2 { private Data3[] theHeap; private int itemsInArray = 0; private int maxSize; public Heap2(int maxSize) { this.maxSize = maxSize; theHeap = new Data3[maxSize]; } public void insert(int index, Data3 newData) { theHeap[index] = newData; itemsInArray++; } // Old Tree Generation Code public void printTree(int rows) { int spaces = 0; int iteration = 1; while (iteration <= rows) { int indent = (int) Math .abs(((Math.pow(-2, -iteration)) * (-16 + (Math.pow(2, iteration))))); int indexToPrint = (int) (.5 * (-2 + (Math.pow(2, iteration)))); int itemsPerRow = (int) (Math.pow(2, iteration - 1)); int maxIndexToPrint = indexToPrint + itemsPerRow; for (int j = 0; j < indent; j++) System.out.print(" "); for (int l = indexToPrint; l < maxIndexToPrint; l++) { System.out.print(theHeap[l].key); for (int k = 0; k < spaces; k++) System.out.print(" "); } spaces = indent; iteration++; System.out.println(); } } public void printTree2(int rows) { // Number of spaces between items in tree int spaces = 0; int iteration = 1; // Generate all of the indents that are // needed depending on the number of rows // to print int[] indent = getIndentArray(rows); while (iteration <= rows) { // Find first Index : .5 * (-2 + 2^n) int indexToPrint = (int) (.5 * (-2 + (Math.pow(2, iteration)))); // Number of Items per Row : 2^(n - 1) int itemsPerRow = (int) (Math.pow(2, iteration - 1)); int maxIndexToPrint = indexToPrint + itemsPerRow; /* * System.out.println("Indent: " + indent[iteration - 1]); * System.out.println("indexToPrint: " + indexToPrint); * System.out.println("itemsPerRow: " + itemsPerRow); * System.out.println("maxIndexToPrint: " + maxIndexToPrint); */ // Print the indents needed for (int j = 0; j < indent[iteration - 1]; j++) System.out.print(" "); // Print all of the index values for each row // indexToPrint represents the first index in the // row, while maxIndexToPrint equals the last for (int l = indexToPrint; l < maxIndexToPrint; l++) { // If the array isn't full don't try to print // indexes that don't exist if (l < itemsInArray) { System.out.print(String.format("%02d", theHeap[l].key)); for (int k = 0; k < spaces; k++) System.out.print(" "); } } // In a tree the spaces get bigger in the // same way that indents get smaller spaces = indent[iteration - 1]; iteration++; System.out.println(); } } // Calculate each indent per row for the tree // then reverse their order to go from biggest // to smallest public int[] getIndentArray(int rows) { int[] indentArray = new int[rows]; for (int i = 0; i < rows; i++) { indentArray[i] = (int) Math.abs((-2 + (Math.pow(2, i + 1)))); } Arrays.sort(indentArray); indentArray = reverseArray(indentArray); return indentArray; } // Reverse the indent values in the array // so that they go from biggest to smallest public int[] reverseArray(int[] theArray) { // Index of the first element int leftIndex = 0; // Index of last element int rightIndex = theArray.length - 1; while (leftIndex < rightIndex) { // Exchange the left and right elements int temp = theArray[leftIndex]; theArray[leftIndex] = theArray[rightIndex]; theArray[rightIndex] = temp; // Move the indexes to check towards the middle leftIndex++; rightIndex--; } return theArray; } // Fill the heap with random numbers based on // the number that is passed in public void generateFilledArray(int randNum) { Data3 randomData1; for (int i = 0; i < this.maxSize; i++) { randomData1 = new Data3((int) (Math.random() * randNum) + 1); this.insert(i, randomData1); } } public static void main(String args[]) { System.out.println("OLD TREE"); Heap2 newHeap = new Heap2(70); // If I generate 2 digit numbers nothing lines up // newHeap.generateFilledArray(90); newHeap.generateFilledArray(9); // If I increase to over 4 rows the spaces are lost in the last row // newHeap.printTree(5); // newHeap.printTree(6); System.out.println("\nNEW TREE\n"); newHeap.printTree2(6); } } class Data3 { public int key; public Data3(int key) { this.key = key; } }

Hey darek,

are you gonna show us how to solve basic problems (ie. reverse a number, palindrome number and so on..)

these kind of questions asked in interviews many of times.

At some point I want to make a tutorial that is just about questions like that. I think that would be great fun! I did that a little bit in my refactoring tutorial

Hi Derek, great stuff you are doing here. As I mentioned on YouTube I covered your tutorials on my website. You can find them here (since Facebook started asking money for leaving messages since today, I am letting you know here! ðŸ™‚ )

http://wordpressexamples.com/web-page-design-tutorial-and-create-a-wordpress-theme2/

Do well man! Love your stuff.

Thank you very much ðŸ™‚ I greatly appreciate you doing that

AMAZING! My teacher can’t do half what you did here.

Thank you ðŸ™‚ I’m very happy that I was able to help.

Is this the best way to solve any computational problems.

In my object oriented design tutorial I cover how I turn a problem into finished code. I hope it helps ðŸ™‚