if not root:
return []
# 先正向层序遍历
result_forward = []
node_current_layer, node_next_layer = deque(), deque()
node_current_layer.append(root)
node_current_data = []
while node_current_layer or node_next_layer:
node = node_current_layer.popleft()
node_current_data.append(node.val)
if node.left:
node_next_layer.append(node.left)
if node.right:
node_next_layer.append(node.right)
if not node_current_layer:
node_current_layer = node_next_layer
node_next_layer = deque()
result_forward.append(node_current_data)
node_current_data = []
return result_forward[::-1]
if __name__ == '__main__':
tree = buildTree([3, 9, 20, 'null', 'null', 15, 7])
print(Solution().levelOrderBottom(tree))
# self.right = None
class Solution:
def findFatherRecur(self, root, p, q):
if (root.val < p.val and root.val > q.val
or root.val > p.val and root.val < q.val):
return root
if root.val == p.val or root.val == q.val:
return root
if root.val < p.val and root.val < q.val:
return self.findFatherRecur(root.right, p, q)
else:
return self.findFatherRecur(root.left, p, q)
def lowestCommonAncestor(self, root, p, q):
"""
:type root: TreeNode
:type p: TreeNode
:type q: TreeNode
:rtype: TreeNode
"""
return self.findFatherRecur(root, p, q)
if __name__ == '__main__':
tree = buildTree([6, 2, 8, 0, 4, 7, 9, 'null', 'null', 3, 5])
p, q = TreeNode(2), TreeNode(8)
print(Solution().lowestCommonAncestor(tree, p, q))
self.sumNumbersRecur(root.right, cur_num)
else:
self._path_sum += cur_num
def sumNumbers(self, root):
"""
:type root: TreeNode
:rtype: int
"""
if not root:
return 0
cur_num = root.val
if root.left and root.right:
self.sumNumbersRecur(root.left, cur_num)
self.sumNumbersRecur(root.right, cur_num)
elif root.left:
self.sumNumbersRecur(root.left, cur_num)
elif root.right:
self.sumNumbersRecur(root.right, cur_num)
else:
self._path_sum += cur_num
return self._path_sum
if __name__ == '__main__':
tree = buildTree([1, 2, 3])
print(Solution().sumNumbers(tree))
if not root:
return
self.getMinimumDifferenceRecur(root.left, data)
data.append(root.val)
self.getMinimumDifferenceRecur(root.right, data)
def getMinimumDifference(self, root):
"""
:type root: TreeNode
:rtype: int
"""
data = []
self.getMinimumDifferenceRecur(root, data)
min_diff = float('inf')
for i in range(1, len(data)):
if data[i] - data[i - 1] < min_diff:
min_diff = data[i] - data[i - 1]
return min_diff
if __name__ == '__main__':
nums = [1, 'null', 3, 2]
root = buildTree(nums)
print(Solution().getMinimumDifference(root))
:type root: TreeNode
:rtype: bool
"""
last_layer_flag = False
cur_layer = [root]
while cur_layer:
next_layer = []
for node in cur_layer:
if not node:
last_layer_flag = True
continue
if last_layer_flag:
return False
next_layer.append(node.left)
next_layer.append(node.right)
cur_layer = next_layer
return True
if __name__ == '__main__':
tree = buildTree([1,2,3,4,5,6])
print(Solution().isCompleteTree(tree))
# class TreeNode:
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution:
def invertTree(self, root):
"""
:type root: TreeNode
:rtype: TreeNode
"""
if not root:
return None
root.right, root.left = root.left, root.right
if root and root.left:
self.invertTree(root.left)
if root and root.right:
self.invertTree(root.right)
return root
if __name__ == '__main__':
tree = buildTree([4, 2, 7, 1, 3, 6, 9])
tree_reverse = Solution().invertTree(tree)
level_order_traversal(tree_reverse)
from Tree_Method import TreeNode, buildTree
class Solution(object):
def tree2str(self, t):
"""
:type t: TreeNode
:rtype: str
"""
if not t: return ""
s = str(t.val)
if t.left or t.right:
s += "(" + self.tree2str(t.left) + ")"
if t.right:
s += "(" + self.tree2str(t.right) + ")"
return s
if __name__ == '__main__':
tree = buildTree([1,2,3,'null',4])
print(Solution().tree2str(tree))
from collections import deque
from Tree_Method import TreeNode,buildTree
class Solution:
def dfs(self, node, i, depth, leftmosts):
if not node:
return 0
if depth >= len(leftmosts):
leftmosts.append(i)
return max(i - leftmosts[depth] + 1, self.dfs(node.left, i * 2, depth + 1, leftmosts),self.dfs(node.right, i * 2 + 1, depth + 1, leftmosts))
def widthOfBinaryTree(self, root):
"""
:type root: TreeNode
:rtype: int
"""
leftmosts = []
return self.dfs(root, 1, 0, leftmosts)
if __name__ == '__main__':
# tree = buildTree([1,1,1,1,'null','null',1,1,'null','null','null','null','null','null',1])
tree = buildTree([1,3,2,5,3,'null',9])
print(Solution().widthOfBinaryTree(tree))
# class TreeNode:
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution:
def flipEquivReccur(self, root1, root2):
if not root1 and not root2:
return True
if (not root1 and root2) or (root1 and not root2):
return False
if root1.val != root2.val:
return False
return (self.flipEquivReccur(root1.left, root2.left) and self.flipEquivReccur(root1.right, root2.right)) or \
(self.flipEquivReccur(root1.left, root2.right) and self.flipEquivReccur(root1.right, root2.left))
def flipEquiv(self, root1, root2):
"""
:type root1: TreeNode
:type root2: TreeNode
:rtype: bool
"""
return self.flipEquivReccur(root1, root2)
if __name__ == '__main__':
tree1 = buildTree([1,2,3,4,5,6,'null','null','null',7,8])
tree2 = buildTree([1,3,2,'null',6,4,5,'null','null','null','null',8,7])
print(Solution().flipEquiv(tree1, tree2))
if root.left:
path.append(root.left)
self.binaryTreePathsRec(root.left, path, result)
path.pop()
if root.right:
path.append(root.right)
self.binaryTreePathsRec(root.right, path, result)
path.pop()
def binaryTreePaths(self, root):
"""
:type root: TreeNode
:rtype: List[str]
"""
if not root:
return []
result = []
path = []
path.append(root)
self.binaryTreePathsRec(root, path, result)
return result
if __name__ == '__main__':
tree = buildTree([1, 2, 3, "null", 5])
print(Solution().binaryTreePaths(tree))
return False
else:
if not root2.left and not root2.right:
return True
else:
return False
def flipEquiv(self, root1, root2):
"""
:type root1: TreeNode
:type root2: TreeNode
:rtype: bool
"""
if not root1 and not root2:
return True
elif root1 and not root2:
return False
elif root2 and not root1:
return False
elif root1.val == root2.val:
return self.flipEquivRecur(root1, root2)
else:
return False
if __name__ == '__main__':
tree1 = buildTree([0, 2, 1, 'null', 3, 'null', 5, 'null', 4])
tree2 = buildTree([0, 'null', 2, 3, 'null', 'null', 4])
# level_order_traversal(tree1)
# level_order_traversal(tree2)
print(Solution().flipEquiv(tree1, tree2))