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| id | title | author | description |
|---|---|---|---|
| data-types | Data Types | Darren Yao | Learn about the basic data types needed for competitive programming. |
There are several main data types that are used in contests: 64-bit integers, floating point numbers, booleans, characters, and strings. Assuming that you are familiar with the language you are using, this should be mostly review.
It's a good idea to use 64-bit integers (long long in C++) instead of 32-bit integers (int). 64-bit integers are less likely to have overflow issues, since they can store any number between -9\,223\,372\,036\,854\,775\,808 and 9\,223\,372\,036\,854\,775\,807 which is roughly equal to \pm 9 \times 10^{18}. Contest problems are usually set such that the 64-bit integer is sufficient. Of course, you shouldn't do this when time and/or memory limits are tight, which may be the case in higher divisions of USACO.
Floating point numbers are used to store decimal values. It is important to know that floating point numbers are not exact, because the binary architecture of computers can only store decimals to a certain precision. Hence, we should always expect that floating point numbers are slightly off. Contest problems will accommodate this by either asking for the greatest integer less than 10^k times the value, or will mark as correct any output that is within a certain \epsilon of the judge's answer. (what's epsilon?)
Boolean variables have two possible states: true and false. We'll usually use booleans to mark whether a certain process is done, and arrays of booleans to mark which components of an algorithm have finished.
Character variables represent a single Unicode character. They are returned when you access the character at a certain index within a string. Characters are represented using the ASCII standard, which assigns each character to a corresponding integer. This allows us to do arithmetic with them; for example, both cout << ('f' - 'a'); in C++ and System.out.print('f' - 'a'); in Java will print 5.
Strings are stored as an array of characters. You can easily access the character at a certain index and take substrings of the string. String problems on USACO Bronze or Silver generally don't involve any special data structures.
Additional Reading
- CPH 1.1 - 1.3
- PAPC Ch 2