99 Clojure Problems – 62B: Collect the Nodes at a Given Level in a List.

"A node of a binary tree is at level N if the path from the root to the node has length N-1. The root node is at level 1. Write a method at-level to collect all nodes at a given level in a list."

(deftest p62b-at-level
  (is (= '(b c) (at-level '[a [b nil nil] [c [d nil nil] [e nil nil]]] 2))))

The basic idea for the solution was to see the tree as a list of nodes and to realise that the nodes at a given level start at node 2^(level - 1) and that this is also the size of each level. Solution on Github.

Read more about this series.