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move-sub-tree-of-n-ary-tree.py
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move-sub-tree-of-n-ary-tree.py
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# Time: O(n)
# Space: O(h)
# Definition for a Node.
class Node(object):
def __init__(self, val=None, children=None):
self.val = val
self.children = children if children is not None else []
# one pass solution without recursion
class Solution(object):
def moveSubTree(self, root, p, q):
"""
:type root: Node
:type p: Node
:type q: Node
:rtype: Node
"""
def iter_find_parents(node, parent, p, q, is_ancestor, lookup):
stk = [(1, [node, None, False])]
while stk:
step, params = stk.pop()
if step == 1:
node, parent, is_ancestor = params
if node in (p, q):
lookup[node] = parent
if len(lookup) == 2:
return is_ancestor
stk.append((2, [node, is_ancestor, reversed(node.children)]))
else:
node, is_ancestor, it = params
child = next(it, None)
if not child:
continue
stk.append((2, [node, is_ancestor, it]))
stk.append((1, [child, node, is_ancestor or node == p]))
assert(False)
return False
lookup = {}
is_ancestor = iter_find_parents(root, None, p, q, False, lookup)
if p in lookup and lookup[p] == q:
return root
q.children.append(p)
if not is_ancestor:
lookup[p].children.remove(p)
else:
lookup[q].children.remove(q)
if p == root:
root = q
else:
lookup[p].children[lookup[p].children.index(p)] = q
return root
# Time: O(n)
# Space: O(h)
# one pass solution with recursion (bad in deep tree)
class Solution_Recu(object):
def moveSubTree(self, root, p, q):
"""
:type root: Node
:type p: Node
:type q: Node
:rtype: Node
"""
def find_parents(node, parent, p, q, is_ancestor, lookup):
if node in (p, q):
lookup[node] = parent
if len(lookup) == 2:
return True, is_ancestor
for child in node.children:
found, new_is_ancestor = find_parents(child, node, p, q, is_ancestor or node == p, lookup)
if found:
return True, new_is_ancestor
return False, False
lookup = {}
is_ancestor = find_parents(root, None, p, q, False, lookup)[1]
if p in lookup and lookup[p] == q:
return root
q.children.append(p)
if not is_ancestor:
lookup[p].children.remove(p)
else:
lookup[q].children.remove(q)
if p == root:
root = q
else:
lookup[p].children[lookup[p].children.index(p)] = q
return root
# Time: O(n)
# Space: O(h)
# two pass solution without recursion
class Solution2(object):
def moveSubTree(self, root, p, q):
"""
:type root: Node
:type p: Node
:type q: Node
:rtype: Node
"""
def iter_find_parents(node, parent, p, q, lookup):
stk = [(1, [node, None])]
while stk:
step, params = stk.pop()
if step == 1:
node, parent = params
if node in (p, q):
lookup[node] = parent
if len(lookup) == 2:
return
stk.append((2, [node, reversed(node.children)]))
else:
node, it = params
child = next(it, None)
if not child:
continue
stk.append((2, [node, it]))
stk.append((1, [child, node]))
def iter_is_ancestor(node, q):
stk = [(1, [node])]
while stk:
step, params = stk.pop()
if step == 1:
node = params[0]
stk.append((2, [reversed(node.children)]))
else:
it = params[0]
child = next(it, None)
if not child:
continue
if child == q:
return True
stk.append((2, [it]))
stk.append((1, [child]))
return False
lookup = {}
iter_find_parents(root, None, p, q, lookup)
if p in lookup and lookup[p] == q:
return root
q.children.append(p)
if not iter_is_ancestor(p, q):
lookup[p].children.remove(p)
else:
lookup[q].children.remove(q)
if p == root:
root = q
else:
lookup[p].children[lookup[p].children.index(p)] = q
return root
# Time: O(n)
# Space: O(h)
# two pass solution with recursion (bad in deep tree)
class Solution2_Recu(object):
def moveSubTree(self, root, p, q):
"""
:type root: Node
:type p: Node
:type q: Node
:rtype: Node
"""
def find_parents(node, parent, p, q, lookup):
if node in (p, q):
lookup[node] = parent
if len(lookup) == 2:
return True
for child in node.children:
if find_parents(child, node, p, q, lookup):
return True
return False
def is_ancestor(node, q):
for child in node.children:
if node == q or is_ancestor(child, q):
return True
return False
lookup = {}
find_parents(root, None, p, q, lookup)
if p in lookup and lookup[p] == q:
return root
q.children.append(p)
if not is_ancestor(p, q):
lookup[p].children.remove(p)
else:
lookup[q].children.remove(q)
if p == root:
root = q
else:
lookup[p].children[lookup[p].children.index(p)] = q
return root