12.6. Base Case Practice¶

A recursive method contains a call to itself. The recursion stops when a base case test is true and a value is returned.

12-5-1: Click on the line or lines that contain the test for the base caseWhen a base case test is true a value is returned and the recursion stops.

public static int factorial(int n)
{
    if (n == 0)
        return 1;
    else
        return n * factorial(n-1);
}

12-5-2: Click on the line or lines that contain the test for the base caseWhen a base case test is true a value is returned and the recursion stops

public static int mystery(int n)
{
    if (n == 0)
        return 1;
    else
        return 2 * mystery (n - 1);
}

12-5-3: Click on the line or lines that contain the test for the base caseWhen a base case test is true a value is returned and the recursion stops

public static int bunnyEars(int bunnies)
{
    if (bunnies == 0) return 0;
    else if (bunnies == 1) return 2;
    else return 2 + bunnyEars(bunnies - 1);
}

12-5-4: Click on the line or lines that contain the test for the base caseWhen a base case test is true a value is returned and the recursion stops

public static void mystery (int x) {
    System.out.print(x % 10);
    if ((x / 10) != 0) {
        mystery(x / 10);
    }
    System.out.print(x % 10);
}

12-5-5: Click on the line or lines that contain the test for the base caseWhen a base case test is true a value is returned and the recursion stops

public static int mystery(String str)
{
    if (str.length() == 1) return 0;
    else
    {
        if (str.substring(0,1).equals("y")) return 1 +
                           mystery(str.substring(1));
         else return mystery(str.substring(1));
      }
   }