Sort Comparisons Counter

Question

I have this code that sorts an array that is filled with random numbers and counts the number comparisons that it takes to complete the sort. I\'m using the sort methods sel

Answer 1

When (or just prior to) the following lines are executed:

• if (intArray[i] > intArray[largestIndex]){
• if(intArray[j-1] > intArray[j]) {
• if(first[iFirst] < second[iSecond]) {

Your mergeSort method uses recursion. As such, it needs to take a comparisons parameter, and pass that down to each subsequent method call and receive the resulting value back again.

public static int mergeSort(int[] intArray, int comparisons) {

    if(intArray.length >= 2) {

        int mid = intArray.length / 2;
        //Create 2 arrays to store half of the data in each
        int[] first = new int[mid];     //holds first half of array
        int[] second = new int[intArray.length - mid];  //holds second half of array

        for(int i = 0; i < first.length; i++) { 
            first[i] = intArray[i];     
        }

        for(int i = 0; i < second.length; i++) {
            second[i] = intArray[mid+i];
        }

        comparisons = mergeSort(first, comparisons);
        comparisons = mergeSort(second, comparisons);
        comparisons = merge(first, second, intArray, comparisons);     //Merge all together

    }

    return comparisons;
}

//merging first and second halves of mergeSort array
public static int merge(int[] first, int[] second, int[] intArray, int comparisons) {

    int iFirst = 0;
    int iSecond = 0;
    int i = 0; 

    //moving the smaller element into intArray
    while(iFirst < first.length && iSecond < second.length) {

        comparisons++;

        if(first[iFirst] < second[iSecond]) {
            intArray[i] = first[iFirst];
            iFirst++;
        }

        else {
            intArray[i] = second[iSecond];
            iSecond++;
        }
        i++;
    }


    //copying the remaining of first array
    while(iFirst < first.length) {
        intArray[i] = first[iFirst];
        iFirst++; i++; 
    }

    //copying the remaining of second array
    while(iSecond < second.length)
    {
        intArray[i] = second[iSecond];
        iSecond++; i++; 
    } 

    return comparisons;
}