Merge pull request gzc#156 from praveenmylavarapu/master

Fixed a typo

Author: Zhenchao Gan

C12-Binary-Search-Trees/12.2.md

@@ -50,7 +50,7 @@ If a successor has left child, then the left child should be successor. The same
 Consider a binary search tree T whose keys are distinct. Show that if the right subtree of a node x in T is empty and x has a successor y, then y is the lowest ancestor of x whose left child is also an ancestor of x. (Recall that every node is its own ancestor.)
 
 ### `Answer`
-If y is the lowerst ancestor of x whose left child is also an ancestor of x, then x must be the node with the maximum key in the left subtree of y, since if we walk from y to x, we never walk left except at the first step.
+If y is the lowest ancestor of x whose left child is also an ancestor of x, then x must be the node with the maximum key in the left subtree of y, since if we walk from y to x, we never walk left except at the first step.
 
 ### Exercises 12.2-7
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