# Big O Notation

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Learn about Big O notation, an equation that describes how the run time scales with respect to some input variables. This video is a part of HackerRank's Cracking The Coding Interview Tutorial with Gayle Laakmann McDowell. http://www.hackerrank.com/domains/tutorials/cracking-the-coding-interview?utm_source=video&utm_medium=youtube&utm_campaign=ctci

By anonymous 2017-09-20

Change your `targetsFound`

variable to a set.
The reason you use that variable is to look up if a cell has been visited and lookups in lists are slow **O(N)** time. Sets support fast lookup **O(1)** and as such should drastically improve your algorithm's performance.

More information about what O(N) and O(1) mean: https://www.youtube.com/watch?v=v4cd1O4zkGw&t=1s

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By anonymous 2017-09-20

One of the basic assumptions when calculating BigO is to

drop non dominant terms.Using the first example,

So, the BigO is of the form O((n^2) + (n^3)) which would suffice to O(n^3).

You can try using the same technique for the second problem.

If you still have some confusion, have a look at the following video: Big O Notation

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