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# 987. Vertical Order Traversal of a Binary Tree
from collections import defaultdict
"""
given the 'root' of a binary tree, calcuate the vertical order traversal of
the binary tree. for each node at position '(row, col)', its left and right
children will be at positions '(row + 1, col - 1)' and '(row + 1, col + 1)'
respectively. the root of the tree is at '(0, 0)'. the vertical order
traversal of a binary tree is a list of top to bottom ordering for each
column index starting from the leftmost column and ending on the rightmost
column. there may be multiple nodes in the same row and same column. in such
a case, sort these nodes by their values. return the vertical order traversal
of the binary tree
"""
# Definition for a binary tree node.
class TreeNode(object):
def __init__(self, val=0, left=None, right=None):
self.val = val
self.left = left
self.right = right
class Solution(object):
def helper(self, placement, level, root, _dict, limits):
if not root:
return
_dict[placement].append((level, root.val))
limits[0] = min(limits[0], placement)
limits[1] = max(limits[1], placement)
self.helper(placement - 1, level + 1, root.left, _dict, limits)
self.helper(placement + 1, level + 1, root.right, _dict, limits)
def verticalTraversal(self, root):
"""
:type root: Optional[TreeNode]
:rtype: List[List[int]]
"""
_dict = defaultdict(list)
limits = [float("inf"), float("-inf")]
self.helper(0, 0, root, _dict, limits)
ans = []
for i in range(limits[0], limits[1] + 1):
tmp = []
for j in sorted(_dict[i]):
tmp.append(j[1])
ans.append(tmp)
return ans
if __name__ == "__main__":
obj = Solution()
print(obj.verticalTraversal(root=[3, 9, 20, None, None, 15, 7]))
print(obj.verticalTraversal(root=[1, 2, 3, 4, 5, 6, 7]))
print(obj.verticalTraversal(root=[1, 2, 3, 4, 6, 5, 7]))
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