CS201 Review Session

CS201 Review

Q1: http://codingbat.com/prob/p135988

public class array11{
    public static int array11(int[] nums, int index){
    int k = 0;
    if (nums[index] == 11){
        k += 1;
    }
    // base case
    if (index == nums.length-1){
        return k;
    } else {
        // recursive step
        return k + array11(nums, index+1);
    }

}

    public static void main(String[] args){
        int[] a = { 11, 12, 15, 5, 11, 17 };
        System.out.println(array11(a, 0));
    }
}

Q2: http://codingbat.com/prob/p170924

public class replace_pi{

    public static String[] replace(String[] a, int index){

        // checks for pi, changes to 3.14
        if (a[index].equals("pi")){
            a[index] = "3.14";
        }

        // base case
        if (a.length-1 == index){
            return a;
        } else {
            // recursive step
            return replace(a, index+1);
        }
    }

    public static void main(String[] args){
        // initial array
        String[] a = { "pi", "apple_pie", "banana_pie", "pi", "pip", "orange_juice" };
        // changed array
        a = replace(a, 0);

        // start creating suitable string representation
        String strng = "{ ";
        for (int i = 0; i < a.length; i++){
            strng += (a[i] + ", ");
        }
        // replaces last ',\ '
        strng = strng.substring(0, strng.length() -2);
        strng += " }";
        System.out.println(strng);
    }
}