Question

I need to create a recursive Boolean method named isMemeber. The method should accept two arguments ONLY: an array and a value. The method should return true if the value is found in the array, or false if the value is not found in the array.

I think that the base case will be if the passed array is empty, but I need help with the recursive case:

public static boolean isMember(int[] array, int value)
{
    if(array.length==0){
        return false; 
    }else{
        return isMember(???);           
    }
}

Here is how it looks with position variable:

public static boolean isMember(int[] array, int value, int position)
{
    if (position > -1)
    {

        if (array[position] == value)
        {
            return true;
        }
        else
        {
            return isMember(array, value, position - 1);
        }
    }
    return false;

}

Answer 1

If you need to use recursion you can copy the array on each recursion. This is inefficent, but using recursion is inefficient compared with using a loop. e.g. Arrays.indexOf()

public static boolean isMember(int[] array, int value) {
    if(array.length == 0) return false; 
    if(array[0] == value) return true;
    int[] array2 = new int[array.length-1];
    System.arraycopy(array,1,array2,0,array2.length);
    return isMember(array2, value);           
}