擅长:python、mysql、java
<p>每当在树上发现问题时,只要使用递归:D</p>
<pre><code>def paths(tree):
#Helper function
#receives a tree and
#returns all paths that have this node as root and all other paths
if tree is the empty tree:
return ([], [])
else: #tree is a node
root = tree.value
rooted_paths = [[root]]
unrooted_paths = []
for subtree in tree.children:
(useable, unueseable) = paths(subtree)
for path in useable:
unrooted_paths.append(path)
rooted_paths.append([root]+path)
for path in unuseable:
unrooted_paths.append(path)
return (rooted_paths, unrooted_paths)
def the_function_you_use_in_the_end(tree):
a,b = paths(tree)
return a+b
</code></pre>