Update diameterOfTree.py

Author: Amogh Singhal

diameterOfTree.py

@@ -1,13 +1,25 @@
 # The diameter of a tree (sometimes called the width) 
 # is the number of nodes on the longest path between 
-# two end nodes.
+# two end nodes(leftmost leaf node and rightmost leaf node).
 
 # The diameter of a tree T is the largest of the following quantities:
-
-# * the diameter of T’s left subtree
-# * the diameter of T’s right subtree
-# * the longest path between leaves that goes through the 
-#   root of T (this can be computed from the heights of the subtrees of T)
+# the diameter of T’s left subtree
+# the diameter of T’s right subtree
+# the longest path between leaves that goes through the root of T (this can be computed from the heights of the subtrees of T)
+
+# Algorithm:
+# Case 1: if the diameter passes through origin, then diameter is
+# height of left subtree + height of right subtree + 1 (root node)
+# d = lheight + rheight + 1
+
+# Case 2: if the diameter is not passing through origin
+# Search for diameter in the left subtree and right subtree
+# Pick the larger value of the two subtrees
+# d = max(ldiameter, rdiameter)
+
+# Finally take max of the two values since we do not 
+# know if diameter is passing through the root or not
+# d = max(lheight + rheight + 1, max(ldiameter, rdiameter))
 
 class Node(object):
   def __init__(self, data):