stack.append(p.right)
stack.append(q.left)
return True
# Recursive Solution
def isSymmetric_recursively(root):
if not root:
return True
return symmetric(root.left, root.right)
# Time: O(n)
# Space: O(h)
def symmetric(left, right):
if left is None and right is None:
return True
if left is None or right is None or left.val != right.val:
return False
return symmetric(left.left, right.right) and symmetric(
left.right, right.left)
if __name__ == '__main__':
# root = dt.deserialize('[2,1,3,0,7,9,1,2,null,1,0,null,null,8,8,null,null,null,null,7]')
root = dt.deserialize('[1,2,2,3,4,4,3]')
# root = dt.deserialize('[1,2,3]')
res = isSymmetric(root)
print(res)
# return True
# # left OR right
# # A + B == TOTAL => A = TOTAL - B
# return hasPathSum_iteratively(root.left, target-root.val) \
# or hasPathSum_iteratively(root.right, target - root.val)
# =============================================================================
return helper(root, target, 0)
def helper(node, target, total):
if node is None:
return False
total += node.val
if node.left is None and node.right is None and total == target:
return True
left = helper(node.right, target, total)
right = helper(node.left, target, total)
return left or right
# return left or right
# return helper(node.right, target, total + node.val) or helper(node.left, target, total + node.val)
if __name__ == '__main__':
# root = dt.deserialize('[2,1,3,0,7,9,1,2,null,1,0,null,null,8,8,null,null,null,null,7]')
# root = dt.deserialize('[1,2,2,3,4,4,3]')
# root = dt.deserialize('[5,4,8,11,null,13,4,7,2,null,null,null,1]')
root = dt.deserialize('[-2,null,-3]')
res = hasPathSum_iteratively(root, -5)
print(res)
nextLevel.append(node.left)
if node.right is not None:
nextLevel.append(node.right)
res.append(level)
current = nextLevel
return res
def levelOrder2(root):
if not root:
return []
visited = []
level = [root]
while level:
visited.append([node.val
for node in level]) # expend() will unpack nested list
level = [
child for node in level for child in (node.left, node.right)
if child
]
return visited
if __name__ == '__main__':
root = dt.deserialize(
'[2,1,3,0,7,9,1,2,null,1,0,null,null,8,8,null,null,null,null,7]')
res = levelOrder2(root)
for i in res:
print(i)
# for node in current:
# if node.left:
# next_level.append(node.left)
# if node.right:
# next_level.append(node.right)
# current = next_level
# =============================================================================
current = [child for node in current for child in (node.left, node.right) if child]
return level
# Time O(n)
# Space O(h) h is the height of the binary tree
def maxDepth_recursively(root):
if not root:
return 0
# =============================================================================
# max_left = maxDepth_recursively (root.left) + 1
# max_right = maxDepth_recursively(root.right) + 1
# return max(max_left, max_right)
# =============================================================================
else:
return max(maxDepth_recursively(root.left), maxDepth_recursively(root.right)) + 1
if __name__ == '__main__':
# root = dt.deserialize('[2,1,3,0,7,9,1,2,null,1,0,null,null,8,8,null,null,null,null,7]')
root = dt.deserialize('[3,9,20,null,null,15,7]')
res = maxDepth_recursively(root)
print(res)