CSCI-1200 Computer Science II — Fall 2006
Lab 8 — Recursion I
Checkpoint 1
Here is a silly pair of mutually-recursive functions:
bool Odd(int number);
bool Even(int number) {
if (!Odd(number)) return true;
else return false;
}
bool Odd(int number) {
if (!Even(number)) return true;
else return false;
}
Type this code into your programming environment and try it out. Use the debugger to see what goes
wrong. Rewrite the code, but you are only allowed to use subtraction and testing if something is equal to
zero. Also Odd cannot directly call itself and Even cannot directly call itself.
To complete this checkpoint: Show a TA what goes wrong in the original version and how you fixed the
problem.
Checkpoint 2
Study the recursive definition below which computes the nth Fibonacci number. Draw the complete acti-
vation record hierarchy that results from the function call fib a(4). This recursion example is complex to
analyze exactly, but find a reasonable upper bound on the number of calls to fib a as a function of n.
int fib_a(int n) {
assert (n >= 0);
if (n == 0) return 1;
if (n == 1) return 1;
return fib_a(n-1) + fib_a(n-2);
}
To complete this checkpoint: Show a TA your diagram and analysis.