print-binary-tree.py

# Time:  O(h * 2^h)
# Space: O(h * 2^h)

# Print a binary tree in an m*n 2D string array following these rules:
#
# The row number m should be equal to the height of the given binary tree.
# The column number n should always be an odd number.
# The root node's value (in string format) should be put in the exactly middle of the first row it can be put.
# The column and the row where the root node belongs will separate the rest space into two parts
# (left-bottom part and right-bottom part). You should print the left subtree in the left-bottom part and
# print the right subtree in the right-bottom part. The left-bottom part and the right-bottom part should have the same size.
# Even if one subtree is none while the other is not, you don't need to print anything for the none subtree
# but still need to leave the space as large as that for the other subtree. However, if two subtrees are none,
# then you don't need to leave space for both of them.
# Each unused space should contain an empty string "".
# Print the subtrees following the same rules.
# Example 1:
# Input:
#      1
#     /
#    2
# Output:
# [["", "1", ""],
#  ["2", "", ""]]
# Example 2:
# Input:
#      1
#     / \
#    2   3
#     \
#      4
# Output:
# [["", "", "", "1", "", "", ""],
#  ["", "2", "", "", "", "3", ""],
#  ["", "", "4", "", "", "", ""]]
# Example 3:
# Input:
#       1
#      / \
#     2   5
#    / 
#   3 
#  / 
# 4 
# Output:
#
# [["",  "",  "", "",  "", "", "", "1", "",  "",  "",  "",  "", "", ""]
#  ["",  "",  "", "2", "", "", "", "",  "",  "",  "",  "5", "", "", ""]
#  ["",  "3", "", "",  "", "", "", "",  "",  "",  "",  "",  "", "", ""]
#  ["4", "",  "", "",  "", "", "", "",  "",  "",  "",  "",  "", "", ""]]
# Note: The height of binary tree is in the range of [1, 10].
#   
# 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 printTree(self, root):
        """
        :type root: TreeNode
        :rtype: List[List[str]]
        """
        def getWidth(root):
            if not root:
                return 0
            return 2 * max(getWidth(root.left), getWidth(root.right)) + 1

        def getHeight(root):
            if not root:
                return 0
            return max(getHeight(root.left), getHeight(root.right)) + 1
            
        def preorderTraversal(root, level, left, right, result):
            if not root:
                return
            mid = left + (right-left)/2
            result[level][mid] = str(root.val)
            preorderTraversal(root.left, level+1, left, mid-1, result)
            preorderTraversal(root.right, level+1, mid+1, right, result)

        h, w = getHeight(root), getWidth(root)
        result = [[""] * w for _ in xrange(h)]
        preorderTraversal(root, 0, 0, w-1, result)
        return result