Traverse tree and return a node instance after n traversals in python
The end goal is to copy a node from one tree to another tree. I want to visit each node in a binary tree and return a node instance after a number of traverses. I cannot seem to figure out how to return a specific node. Every time the node returned matches the id of the root node since I pass the root node to the function.
class node():
def __init__(self):
self.parent = None
self.left = None
self.right = None
def randnode(self, target):
global count
if target == count:
# print 'At target', '.'*25, target
return self
else:
if self.left is not None:
count += 1
self.left.randnode(target)
if self.right is not None:
count += 1
self.right.randnode(target)
Asked by: Melissa198 | Posted: 06-12-2021
Answer 1
If you're doing a DFS and counting iterations, you don't even need recursion, just a stack of places to try, and popping/pushing data.
def dfs(self,target):
count = 0
stack = [start]
while stack:
node = stack.pop()
if count == target:
return node
if node is None: # since we push left/right even if None
continue # stop pushing after we hit None node
stack.extend([self.left,self.right])
return -1 # ran out of nodes before count
Bonus points : swapping stack to a queue for BFS
Apart from that, you might want to pass the count as a parameter, like all self-respecting recursive calls, you can make this stateless ;-)
class node():
def __init__(self):
self.parent = None
self.left = None
self.right = None
def randnode(self, target,count=0):
if target == count:
# print 'At target', '.'*25, target
return self
if self.left is not None:
return self.left.randnode(target,count + 1)
if self.right is not None:
return self.right.randnode(target,count + 1)
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