From 236500bc03d18b10f0989e052f4e829b52ad03f0 Mon Sep 17 00:00:00 2001 From: Aleksander Sadikov Date: Fri, 23 Sep 2016 18:49:19 +0200 Subject: English translation for quicksort/2 added. --- prolog/problems/sorting/quick_sort_2/en.py | 59 +++++++++++++++++++++++++++++- 1 file changed, 58 insertions(+), 1 deletion(-) (limited to 'prolog') diff --git a/prolog/problems/sorting/quick_sort_2/en.py b/prolog/problems/sorting/quick_sort_2/en.py index aa3eb44..a5b571b 100644 --- a/prolog/problems/sorting/quick_sort_2/en.py +++ b/prolog/problems/sorting/quick_sort_2/en.py @@ -8,4 +8,61 @@ description = '''\ L = [1,2,3,4,5]. ''' -hint = {} +plan = ['''\ +

Divide and conquer! And use previous solutions, of course. :)

+''', '''\ +

Take the head away, use it as a pivot, divide the tail into smaller and larger elements. Use recursion on +so obtained sublists since both are shorter (in the worst case scenario shorter by just the head element -- +this also explains why quicksort works worst on already sorted lists). In the end simply combine the sublists.

+''', '''\ +

If list L is composed of head P and tail T and if the tail is +split into sublists containing smaller and larger elements, respectively, based on pivot P, and if +we assume the recursion sorts these two sublists into lists SortedSmallerElems and +SortedGreaterElems, and if finally we concatenate these two lists and add in between pivot/head +P, then this results in correctly sorted initial list L.

+'''] + +hint = { + 'eq_instead_of_equ': '''\ +

The operator == is "stricter" than operator = in the sense that +for the latter it is enough to be able to make the two operands equal (unification).

+

Of course, you can also solve the exercise without explicit use of either of these two operators, just +remember that unification is implicitly performed with the predicate's arguments (head of clause).

+''', + + 'eq_instead_of_equ_markup': '''\ +

Perhaps the operator for unification (=) would be better?

+''', + + 'base_case': '''\ +

Did you think of a base case? Which list can you sort without any effort whatsoever?

+''', + + 'recursive_case': '''\ +

The base case is ok. However, what about the general recursive case?

+''', + + 'predicate_always_false': '''\ +

It seems your predicate is always "false". Did you give it the correct name, +or is it perhaps misspelled?

+

If the name is correct, check whether something else is misspelled, perhaps there is a full stop instead of +a comma or vice versa, or maybe you typed a variable name in lowercase?

+

It is, of course, also possible that your conditions are too restrictive, or even impossible to satisfy +(as would be, for example, the condition that X is simultaneously smaller and greater than +Y, or something similarly impossible).

+''', + + 'timeout': '''\ +

Is there an infinite recursion at work here? How will it ever stop?

+

Or perhaps is there a missing, faulty, or simply incompatible (with the general recursive case) base case?

+''', + + 'arbitrary_base_case': '''\ +

How can the sorted list be anything whatsoever or a list with an arbitrary element? Did you use +a variable without an assigned value?

+''', + + 'forgotten_pivot': '''\ +

Did you, perhaps, forgot to put the pivot element back into the list when returning from recursion?

+''', +} -- cgit v1.2.1