Create find-bottom-left-tree-value.py

Author: kamyu104

Python/find-bottom-left-tree-value.py

@@ -0,0 +1,67 @@
+# Time:  O(n)
+# Space: O(h)
+
+# Given a binary tree, find the leftmost value in the last row of the tree.
+#
+# Example 1:
+# Input:
+#
+#     2
+#   / \
+#   1   3
+#
+# Output:
+# 1
+# Example 2: 
+# Input:
+#
+#         1
+#       / \
+#       2   3
+#      /   / \
+#     4   5   6
+#       /
+#       7
+#
+# Output:
+# 7
+# Note: You may assume the tree (i.e., the given root node) is not NULL.
+
+# 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 findBottomLeftValue(self, root):
+        """
+        :type root: TreeNode
+        :rtype: int
+        """
+        def findBottomLeftValueHelper(root, curr_depth, max_depth, bottom_left_value):
+            if not root:
+                return max_depth, bottom_left_value
+            if not root.left and not root.right and curr_depth+1 > max_depth:
+                return curr_depth+1, root.val
+            max_depth, bottom_left_value = findBottomLeftValueHelper(root.left, curr_depth+1, max_depth, bottom_left_value)
+            max_depth, bottom_left_value = findBottomLeftValueHelper(root.right, curr_depth+1, max_depth, bottom_left_value)
+            return max_depth, bottom_left_value
+
+        result, max_depth = 0, 0
+        return findBottomLeftValueHelper(root, 0, max_depth, result)[1]
+
+
+# Time:  O(n)
+# Space: O(n)
+class Solution2(object):
+    def findBottomLeftValue(self, root):
+        """
+        :type root: TreeNode
+        :rtype: int
+        """
+        queue = [root]
+        for node in queue:
+            queue += filter(None, (node.right, node.left))
+        return node.val