1. From Recursion To Iteration: A Case Study
COMP 212
Spring 2007

2. ASorter’s sort() method
public final void sort(Object[] A, int lo, int hi) {
if (lo < hi) {
int s = split(A, lo, hi);
sort(A, lo, s-1);
sort(A, s, hi);
join(A, lo, s, hi); }

3. A Pathological Case size = n A: sort sort size = n -1 size = 1 sort…

4. How Does Recursion Work?
Method Execution Stack
main
Stack frame:
sort
sort
sort
Method parameters,
Local variables,
Who called whom
split

5. Solutions?
Tail-recursion elimination
Iteration …

6. Tail Recursion int fibHelper(int i, int current, int next) {
if (i == 0)
return current;
else
return fib(i - 1, next, current + next); }
int fib(int i) {
return fibHelper(I, 0, 1);