While reading the &quot;Cracking the coding interview&quot; I learned that all recursive problems can be solved iteratively. I can't get my head around the statement. To me, the only option left is that of brute force search. So, is there a general methodology to convert a recursive problem to an iterative one efficiently? e.g. How would one do it for merge-sort? It has complexity O(nlog(n)) in recursion. How'd one solve it iteratively?
I've used recursion quite a lot on my many years of programming to solve simple problems, but I'm fully aware that sometimes you need iteration due to memory/speed problems.  So, sometime in the very far past I went to try and find if there existed any "pattern" or text-book way of transforming a common recursion approach to iteration and found nothing. Or at least nothing that I can remember it would help.   Are there general rules? Is there a "pattern"?
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