Recursion

1
Recursion

• State the problem recursively
• A well-defined base case
• A recursive call that guarantees a smaller
  problem and eventually leads to the base case.
• If no base case specified, or you never reach the
  base case, youll have infinite recursion.
• For the recursive call, consider whether what
  actions (if any) need to be performed, and
  whether the action happens before or after the
  recursive call.

2
Recursion - xn

• Write a method Power(x,n) which returns xn
• Base case xn x, if n 1
• Recursive cases xn x xn-1, if ngt1

3
Recursion output digits

• Take an integer, write the digits one at a time
  on separate lines.
• WriteDigits(1234), output
• 1
• 2
• 3
• 4
• Base case
• Output n, for n lt 10
• Recursive case
• Output digits of (n/10), then output n10, for
  ngt10.
• What if we want to output the digits in a reverse
  order?

4
About the test

• Review session on Wed.
• Polymorphism, exception handling, recursion.
• C windows controls.
• Zhihongs office hours
• Tue Thur 400P 530P
• Thur 1030P 1220P (NO discussion!)