Question

Could you please check what is wrong with this program?

The output should be

answer is: 4
kSmall answer is: 4
answer is: 11
kSmall answer is: 11

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#include <iomanip>

#include <iostream>

#include <string>

using namespace std;

int const ARRAY_SIZE = 6;

int pivotIndex;

int p;

int kSmall(int k, int anArray[], int first, int last)

{

if (k < pivotIndex - first + 1)

return kSmall(k, anArray, first, pivotIndex - 1);

else if (k == pivotIndex - first + 1)

return p;

else

return kSmall(k - (pivotIndex - first + 1), anArray, pivotIndex + 1, last);

}

int main()

{

int testArray1[] = {6,3,1,2,4,5};

int position = 4;

int pivotIndex=4;

//int p=pivotIndex;

cout << "answer is: 4" << endl << "kSmall answer is: " << kSmall(position, testArray1, 0, ARRAY_SIZE -1) << endl;

int testArray2[] = {20,11,12,-45,7,18};

position = 3;

pivotIndex=12;

cout << "answer is: 11" << endl << "kSmall answer is: " << kSmall(position, testArray2, 0, ARRAY_SIZE -1) << endl;

}

Answer 1

The solution of the above problem can be given as below:

Output Screen:

/*Sourrce code */
#include <iostream>
#include <string>
#include <iomanip>

using namespace std;

int const ARRAY_SIZE = 6;

/*Function Prototype */
int partition(int Array[], int left, int right);

/*Swap Function */
void swap(int *firstNumber, int *secondNumber)
{
    int temp = *firstNumber;
    *firstNumber = *secondNumber;
    *secondNumber = temp;
}

/*Partition Function */
int partition(int Array[], int left, int right)
{
    int x = Array[right], i = left - 1;
    for (int j = left; j <= right - 1; j++)
    {
        if (Array[j] < x)
        {
            i++;
            swap(&Array[j], &Array[i]);
        }
    }
    swap(&Array[i+1], &Array[right]);
    return (i+1);
}

int kSmall(int k, int anArray[], int first, int last)
{
    /*Mistake - II Bound Condition */
    if (k > 0 && k <= ARRAY_SIZE){

        /*Mistake - I : PivotElement is never calculated */
        int pivotIndex = partition(anArray,first,last);

        /*return the pivotElement because that is present
         * at its sorted position */
        if (k - 1 == pivotIndex )
            return anArray[pivotIndex];

        /*if position is less than pivot then recurse in left subArray */
        if (pivotIndex > k-1)
            return kSmall(k,anArray, first, pivotIndex-1);

        /*if position is greater than pivot then recurse in right subArray */
        else
            return kSmall(k , anArray, pivotIndex + 1, last);
    }
    /*If out of bound position is being entered */
    return INT_MAX;
}

int main()
{
    int testArray1[] = {6,3,1,2,4,5};

    /*Which smallest number to find */
    int position = 4;

    cout << "answer is: 4" << endl << "kSmall answer is: "
         << kSmall(position, testArray1, 0, ARRAY_SIZE - 1) << endl;

    int testArray2[] = {20,11,12,-45,7,18};

    /*Which smallest number to find */
    position = 3;

    cout << "answer is: 11" << endl << "kSmall answer is: "
         << kSmall(position, testArray2, 0, ARRAY_SIZE - 1) << endl;

}

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