1. 111. Minimum Depth of Binary Tree

    # Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def minDepth(self, root):
        """
        :type root: TreeNode
        :rtype: int
        """
        return self.depth(root, layer=0)

    def depth(self, root, layer):
        if root == None:
            return layer ...
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  2. 110. Balanced Binary Tree

    # Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def isBalanced(self, root):
        """
        :type root: TreeNode
        :rtype: bool
        """
        if root == None:
            return True
        return abs(self.getHeight(root.left) - self.getHeight(root.right)) < 2 ...
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  3. 109. Convert Sorted List to Binary Search Tree

    # Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.next = None

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def sortedListToBST(self, head):
        """
        :type head: ListNode
        :rtype ...
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  4. 108. Convert Sorted Array to Binary Search Tree

    # Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def sortedArrayToBST(self, nums):
        """
        :type nums: List[int]
        :rtype: TreeNode
        """
        length = len(nums)
        if length == 0:
            return None
        root = TreeNode(nums[length/2])
        root.left ...
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  5. 107. Binary Tree Level Order Traversal II

    # Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def levelOrderBottom(self, root):
        """
        :type root: TreeNode
        :rtype: List[List[int]]
        """
        if root == None:
            return []
        queue = [root]
        result = []
        while queue:
            newq = []
            newr = []
            for item in ...
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  6. 106. Construct Binary Tree from Inorder and Postorder Traversal

    # Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def buildTree(self, inorder, postorder):
        """
        :type inorder: List[int]
        :type postorder: List[int]
        :rtype: TreeNode
        """
        if not postorder:
            return None
        root = TreeNode(postorder[-1])
        pos ...
    read more

  7. 105. Construct Binary Tree from Preorder and Inorder Traversal

    # Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def buildTree(self, preorder, inorder):
        """
        :type preorder: List[int]
        :type inorder: List[int]
        :rtype: TreeNode
        """
        # inorder:DBHEIAFCG
        # preorder:ABDEHICFG
        if not inorder:  # inorder base is ...
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  8. 104. Maximum Depth of Binary Tree

    # Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def maxDepth(self, root):
        """
        :type root: TreeNode
        :rtype: int
        """
        return self.depth(root, layer=0)

    def depth(self, root, layer):
        if root == None:
            return layer ...
    read more

  9. 103. Binary Tree Zigzag Level Order Traversal

    # Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def zigzagLevelOrder(self, root):
        """
        :type root: TreeNode
        :rtype: List[List[int]]
        """
        if root == None:
            return []
        queue = [root]
        result = []
        count = 0
        while queue:
            newq = []
            newr = []
            for ...
    read more

  10. 102. Binary Tree Level Order Traversal

    import Queue
# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def levelOrder(self, root):
        """
        :type root: TreeNode
        :rtype: List[List[int]]
        """
        if root == None:
            return []
        queue = Queue.Queue()
        queue.put(root)  # record each ...
    read more

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