root: 根节点
'''
if root.left:
self.helper(result, root.left)
if root.right:
self.helper(result, root.right)
result.append(root.val)
def post_order_traversal(self, root: TreeNode) -> List[int]:
'''
后序遍历
Args:
res: 链表
root: 根节点
'''
result = []
if not root:
return result
self.helper(result, root)
return result
if __name__ == '__main__':
arr = [1, 2, 3, 4, 5]
tree_node = TreeNode()
tree = tree_node.create_binary_tree_array(arr)
solution = Solution()
result = solution.post_order_traversal(tree)
print(result)
assert result[len(result) - 1] == 1
Returns:
布尔值
'''
queue = []
queue.append(root)
queue.append(root)
while queue:
r1 = queue.pop()
r2 = queue.pop()
if not r1 and not r2:
continue
if not r1 or not r2:
return False
if r1.val != r2.val:
return False
queue.append(r1.left)
queue.append(r2.right)
queue.append(r1.right)
queue.append(r2.left)
return True
if __name__ == '__main__':
arr1 = [1, 2, 2]
tree_node = TreeNode()
root = tree_node.create_binary_tree_array(arr1)
solution = Solution()
result = solution.is_symmetric2(root)
print(result)
assert result == True
result = 0
queue = []
queue_index = []
queue.append(root)
queue_index.append(1)
while len(queue) > 0:
level_size = len(queue)
init_index = queue_index[0]
i = init_index
while level_size > 0:
r = queue.pop(0)
i = queue_index.pop(0)
if r.left:
queue.append(r.left)
queue_index.append(i * 2)
if r.right:
queue.append(r.right)
queue_index.append(i * 2 + 1)
level_size -= 1
result = max(result, i - init_index + 1)
return result
if __name__ == '__main__':
arr = [3, 2, 3, None, 3, None, 1]
node = TreeNode.create_binary_tree_array(arr)
solution = Solution()
result = solution.width_of_binary_tree(node)
print(result)
assert result == 3
'''
if t1 == None:
return t2
if t2 == None:
return t1
stack = []
stack.append((t1, t2))
while stack:
t = stack.pop()
if t[0] == None or t[1] == None:
continue
t[0].val += t[1].val
if t[0].left == None:
t[0].left = t[1].left
else:
stack.append((t[0].left, t[1].left))
if t[0].right == None:
t[0].right = t[1].right
else:
stack.append((t[0].right, t[1].right))
return t1
if __name__ == '__main__':
tree_node = TreeNode()
t1 = tree_node.create_binary_tree_array([1, 2, 3], 0)
t2 = tree_node.create_binary_tree_array([1, 2, 3], 0)
t = merge_trees2(t1, t2)
t_arr = per_order_traversal(t)
print(t_arr)
root: 节点root
p: 节点p
q: 节点q
Returns:
最小公共祖先
'''
if not root:
return root
if not p or not q:
return root
left = lowest_common_ancestor(root.left, p, q)
right = lowest_common_ancestor(root.right, p, q)
if not left and not right:
return None
if left and right:
return root
if not left:
return right
else:
return left
if __name__ == '__main__':
nums = [3, 5, 1, 6, 2, 0, 8, None, None, 7, 4]
tree_node = TreeNode()
p = TreeNode(5)
q = TreeNode(1)
root = tree_node.create_binary_tree_array(nums)
result = lowest_common_ancestor(root, p, q)
print(result)
from tree.tree_node import TreeNode
class Solution:
def tree_2_str(self, root: TreeNode) -> str:
'''
将树转成字符串
Args:
root: 二叉树
Returns:
字符串str
'''
if root == None:
return ''
left = str(self.tree_2_str(root.left))
right = str(self.tree_2_str(root.right))
left = '' if len(left) < 1 and len(right) < 1 else '(' + str(
left) + ')'
right = '' if len(right) < 1 else '(' + str(right) + ')'
return str(root.val) + left + right
if __name__ == '__main__':
nums = [1, 2, 3, 4]
root = TreeNode.create_binary_tree_array(nums)
solution = Solution()
result = solution.tree_2_str(root)
print(result)
assert result == '1(2(4))(3)'