def construct_tree(freqs): # constructs the tree given the frequencies of each character nodes = [HuffmanNode(letter, freqs[letter]) for letter in freqs] # nodes contains the HuffmanNodes trees = [HuffmanTree(node) for node in nodes] h = Heap() for tree in trees: h.insert(tree) # the heap contains all the trees while len(h.elems) > 2: # including 0 t1 = h.minimum() # extract the two least frequent letters h.delete() t2 = h.minimum() h.delete() newTree = combine(t2, t1) # create a new tree combining the two nodes h.insert(newTree) # insert the new tree back into the heap # at this point, the heap contains only one element return h.minimum()
