9. Symbol Tables and Hashing.   

Looking at the binary search, it would seem that there could not possibly be a faster method for searching large structures. This is true if the decisions are made based only on key comparisons. Hashing is a method of order O(1)!


Hashing.
Building.
Searching and Collision Resolution.

Because Hashing is such a fast technique, it is used in the majority of compilers.