Haskell, I assume. Two things really make Haskell shine when it comes to problems like this: 1) higher-order list operations -- you're not iterating through indices, so there is no possibility for off-by-one errors, and 2) immutability -- your code takes a new list with the undesirable elements removed; you can't remove elements of a structure at the same time you're iterating through it.

I always love the problems on SPOJ where they give you the number of cases up front, because in Haskell you can almost always throw out that value. Your map function knows when the list is out of elements.

The snippet I posted can easily be made into a generic function<T> that takes a collection<T> and a predicate<T>. For example, the Apache Commons library offers such a function for Java, so where available the code comes down to the fairly similar

  CollectionUtils.filter(collection, predicate);

Of course aside from being a bit more verbose, predicate needs to be an object (often a singleton), because you can't pass around functions.

It's not as concise as Haskell, but the addition of FP capabilities to C# make it a lot more pleasant as a practical language than it was in earlier days.

var filteredCollection = collection.Where(x => predicate(x));

l = [i for i in l if predicate(i)]