2.3 KiB
| id | title | author |
|---|---|---|
| data | Data Types | Darren Yao |
There are several main data types that are used in contests: 32-bit and 64-bit integers, floating point numbers, booleans, characters, and strings.
Reading
- CPH 1.1 - 1.3
The 32-bit integer supports values between -2\,147\,483\,648 and 2\,147\,483\,647, which is roughly equal to \pm 2 \times 10^9. If the input, output, or \textit{any intermediate values used in calculations} exceed the range of a 32-bit integer, then a 64-bit integer must be used. The range of the 64-bit integer is 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. If it's not, the problem will ask for the answer modulo m, instead of the answer itself, where m is a prime. In this case, make sure to use 64-bit integers, and take the remainder of x modulo m after every step using x %= m;.
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.
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 are generally very easy and don't involve any special data structures.