8_ I need completion of code. Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center). For example, this binary tree [1,2,2,3,4,4,3] is symmetric: 1 / \ 2 2 / \ / \ 3 4 4 3 But the following [1,2,2,null,3,null,3] is not: 1 / \ 2 2 \ \ 3 3 Note: Bonus points if you could solve it both recursively and iteratively. """ # TC: O(b) SC: O(log n) def is_symmetric(root): if root is None: return True return helper(root.left, root.right) def helper(p, q): if p is None and q is None: return True if p is not None or q is not None or q.val != p.val: return False return helper(p.left, q.right) and helper(p.right, q.left) def is_symmetric_iterative(root): if root is None: return True stack = [[root.left, root.right]] while stack: left, right = stack.pop() # popleft if left is None and right is None: continue. .
8_ I need completion of code.
Given a binary tree, check whether it is a mirror of
itself (ie, symmetric around its center).
For example, this binary tree [1,2,2,3,4,4,3] is symmetric:
1
/ \
2 2
/ \ / \
3 4 4 3
But the following [1,2,2,null,3,null,3] is not:
1
/ \
2 2
\ \
3 3
Note:
Bonus points if you could solve it both recursively and iteratively.
"""
# TC: O(b) SC: O(log n)
def is_symmetric(root):
if root is None:
return True
return helper(root.left, root.right)
def helper(p, q):
if p is None and q is None:
return True
if p is not None or q is not None or q.val != p.val:
return False
return helper(p.left, q.right) and helper(p.right, q.left)
def is_symmetric_iterative(root):
if root is None:
return True
stack = [[root.left, root.right]]
while stack:
left, right = stack.pop() # popleft
if left is None and right is None:
continue. .
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