Difference between revisions of "99 questions/Solutions/62"
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<haskell> |
<haskell> |
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internals :: Tree a -> [a] |
internals :: Tree a -> [a] |
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| − | internals Empty = [] |
+ | internals Empty = [] |
internals (Branch a Empty Empty) = [] |
internals (Branch a Empty Empty) = [] |
||
| − | internals (Branch a left right) = |
+ | internals (Branch a left right ) = a : internals left ++ internals right |
</haskell> |
</haskell> |
||
Revision as of 20:23, 20 January 2011
Collect the internal nodes of a binary tree in a list
An internal node of a binary tree has either one or two non-empty successors. Write a predicate internals/2 to collect them in a list.
internals :: Tree a -> [a]
internals Empty = []
internals (Branch a Empty Empty) = []
internals (Branch a left right ) = a : internals left ++ internals right