What is Wrong with my Binary Insertion Code?

Question

I am a beginner in Java trying to create a class that implements the binary insertion sort and sorts out random arrays of the data sizes 50, 500, 5000, 50000, and 500000.

The program works fine when I implemented it as an insertion sort.

public double InsertionSort(long array[]) {
            setType("Insertion Sort");
            long temp;
            int y;
            double numOfSwap = 0, numOfComparisons = 0;
            double startTime = System.nanoTime();
            for (int x = 1; x < array.length; x++) {
                temp = array[x];
                numOfSwap++;
                y = x;
                numOfComparisons++;
                while ((y > 0)) {
                    numOfComparisons++;
                    if ((array[y - 1]) > temp) {
                        array[y] = array[y - 1];
                        numOfSwap++;
                        y = y - 1;
                    } else
                        break;
                }
                array[y] = temp;
                numOfSwap++;
            }
            double endTime = System.nanoTime();
            setSwap(numOfSwap / 3);
            setComparisons(numOfComparisons);
            setTime(endTime - startTime);
            return getTime();

        }

But when I tried to insert a binary search, it did not work anymore.

 public double binaryInsertionSort(long array[], int value, int left, int right) {
            setType("Binary Insertion Sort");
            long temp;
            int y;
            int left, right;
            double numOfSwap = 0, numOfComparisons = 0;
            double startTime = System.nanoTime();
            for (int x = 1; x < array.length; x++) {
                temp = array[x];
                numOfSwqp++;
                int left = y;
                int right = x;
                if (left>right)
                    return -1;
                int middle = (left + right)/2;
                if (array[middle] == value)
                    return middle;
                numOfComparisons++;
                else if (array[middle]>value)
                    return binaryInsertionSort(array, value,left, middle -1);
                numOfComparisons++;
                else
                    return binaryInsertionSort (array, value, middle +1, right);
                numOfComparisons++;
            }
            double endTime = System.nanoTime();
            setSwap(numOfSwap / 3);
            setComparisons(numOfComparisons);
            setTime(endTime - startTime);
            return getTime();
        }

Can someone please help me fix my code?

Answer 1

There were mistakes in your code. I corrected them. First of all your left and right variables are defined in this line :-

public double binaryInsertionSort(long array[], int value, int left, int right)

why are you again defining them inside method body. So I removed their double declaration. Second you assigned value of left variable to y which was wrong. Actually you have to assign value of y toleft. Third error in your code was your method calls were wrong. You defined binaryInsertionSort with four parameters and you were calling it by single parameter so I modified your method calls like this:-

sortTime = binaryInsertionSort(sortedArray,10,20,30);

Rest were minor mistakes. Here is corect code of your `binaryInsertionSort method :-

public double binaryInsertionSort(long array[], int value, int left, int right) {

setType("Binary Insertion Sort");

long temp;

int y=0;

//int left, right;

double numOfSwap = 0, numOfComparisons = 0;

double startTime = System.nanoTime();

for (int x = 1; x < array.length; x++) {

temp = array[x];

numOfSwap++;

y=left;

right = x;

if (left>right){
return -1;
}

int middle = (left + right)/2;

if (array[middle] == value){

    numOfComparisons++;
    return middle;

} else if (array[middle]>value){

    numOfComparisons++;
    return binaryInsertionSort(array, value,left, middle -1);

} else{

    numOfComparisons++;    
    return binaryInsertionSort (array, value, middle +1, right);
    }

}

double endTime = System.nanoTime();

setSwap(numOfSwap / 3);

setComparisons(numOfComparisons);

setTime(endTime - startTime);

return getTime();

}
`

I mailed you complete corrected code of your program. Check your mail box. Acknowledge me whether you find my answer useful or not. Happy Coding :)

Answer 2

Your binary insertion sort code contains numerous errors that your compiler must be telling you about. Your first order of business should be understanding and fixing all of those. Alternatively, many of the problems with the binary insertion sort code appear to arise from it having been made by attempting to adapt the standard insertion sort code. I recommend instead implementing the binary version from scratch. Additionally, implement the sort first; add instrumentation (comparison and swap counts) after the sort itself is working.

Furthermore, there are some distinct oddities in your code:

• it is atypical and not advantageous to implement any version of insertion sort recursively.

• your specific attempt at a recursive implementation does not make sense anyway: the main loop would run only one iteration, and the code after the loop would be dead.

• It's hard to be sure, but I think you've got the whole idea of binary insertion sort wrong. You appear to be trying to split the array into pieces to sort those recursively, like a merge sort or quick sort, but that's not how binary insertion sort works. Binary insertion sort differs from standard insertion sort primarily in that it uses a binary search instead of a linear search to find the insertion position for each element.