selectionProcedure.java

import java.util.*;

public class selectionProcedure {
    // function to do the partition of an array
    public static int partition(int[] arr, int l, int h){
        // first element as the pivot element in an array
        int pivot = arr[l];
        int i = l;
        for(int j=l+1; j<=h; j++){
            if(arr[j] <= pivot){
                i = i + 1;
                // swap(arr[i], arr[j])
                int tem = arr[i];
                arr[i] = arr[j];
                arr[j] = tem;
            }
        }
        // swap (arr[l], arr[i])
        // to get the correct position of the pivot element
        int tem = arr[l];
        arr[l] = arr[i];
        arr[i] = tem;
        // index of the pivot element
        return i;
    }

    public static int selectionProcedure(int[] arr, int l, int h, int k){
        //1. Dividing the problem into subproblems
        int m = partition(arr, l, h);
        // relationship between the index number and the position number
        if(m == k-1){
            return arr[m];
        }

        else if(m < k-1){
            // traverse towards right side of an array
            // 2. Conquer the subproblems via recursion
            return selectionProcedure(arr, m+1, h, k);
        }
        // traverse towards left side of an array
        else return selectionProcedure(arr, l, m-1, k);
    }

     public static void main(String[] args){
        int[] arr = {50, 30, 70, 90, 10, 34, 89, 98, 13};
        int n = arr.length;
        int k = 6;

       
        int result = selectionProcedure(arr, 0, n-1, k);
        System.out.println("The kth smallest element in an array is: "+result);

       

    }
}