|
| 1 | +--- |
| 2 | +Title: 'max_size()' |
| 3 | +Description: 'Returns the maximum number of elements that an unordered_set can theoretically hold.' |
| 4 | +Subjects: |
| 5 | + - 'Code Foundations' |
| 6 | + - 'Computer Science' |
| 7 | +Tags: |
| 8 | + - 'Containers' |
| 9 | + - 'Methods' |
| 10 | + - 'STL' |
| 11 | +CatalogContent: |
| 12 | + - 'learn-c-plus-plus' |
| 13 | + - 'paths/computer-science' |
| 14 | +--- |
| 15 | + |
| 16 | +The **`.max_size()`** member [function](https://www.codecademy.com/resources/docs/cpp/functions) returns the maximum number of elements an `unordered_set` can theoretically hold. This limit depends on the system and the implementation of the standard library, not on actual available memory. |
| 17 | + |
| 18 | +## Syntax |
| 19 | + |
| 20 | +```pseudo |
| 21 | +unordered_set_name.max_size() |
| 22 | +``` |
| 23 | + |
| 24 | +**Parameters:** |
| 25 | + |
| 26 | +This function takes no parameters. |
| 27 | + |
| 28 | +**Return value:** |
| 29 | + |
| 30 | +The method returns a value of type `size_type`, representing the theoretical maximum number of elements. |
| 31 | + |
| 32 | +## Example 1: Basic Usage |
| 33 | + |
| 34 | +In this example, the program prints the maximum number of elements an `unordered_set` can theoretically hold: |
| 35 | + |
| 36 | +```cpp |
| 37 | +#include <iostream> |
| 38 | +#include <unordered_set> |
| 39 | + |
| 40 | +int main() { |
| 41 | + std::unordered_set<int> numbers; |
| 42 | + |
| 43 | + std::cout << "Maximum size: " << numbers.max_size() << std::endl; |
| 44 | + |
| 45 | + return 0; |
| 46 | +} |
| 47 | +``` |
| 48 | + |
| 49 | +The output will be: |
| 50 | + |
| 51 | +```shell |
| 52 | +Maximum size: 1152921504606846975 |
| 53 | +``` |
| 54 | + |
| 55 | +> **Note:** The actual value may vary depending on the system and implementation. |
| 56 | +
|
| 57 | +## Example 2: Using Different Data Types |
| 58 | + |
| 59 | +In this example, the `max_size()` value is shown for `unordered_set` containers holding different [data types](https://www.codecademy.com/resources/docs/cpp/data-types): |
| 60 | + |
| 61 | +```cpp |
| 62 | +#include <iostream> |
| 63 | +#include <unordered_set> |
| 64 | + |
| 65 | +int main() { |
| 66 | + std::unordered_set<int> int_set; |
| 67 | + std::unordered_set<double> double_set; |
| 68 | + std::unordered_set<char> char_set; |
| 69 | + |
| 70 | + std::cout << "int max size: " << int_set.max_size() << std::endl; |
| 71 | + std::cout << "double max size: " << double_set.max_size() << std::endl; |
| 72 | + std::cout << "char max size: " << char_set.max_size() << std::endl; |
| 73 | + |
| 74 | + return 0; |
| 75 | +} |
| 76 | +``` |
| 77 | + |
| 78 | +The output will be: |
| 79 | + |
| 80 | +```shell |
| 81 | +int max size: 1152921504606846975 |
| 82 | +double max size: 1152921504606846975 |
| 83 | +char max size: 1152921504606846975 |
| 84 | +``` |
| 85 | + |
| 86 | +## Codebyte Example |
| 87 | + |
| 88 | +In this example, the program compares the current size of an `unordered_set` with its theoretical maximum: |
| 89 | + |
| 90 | +```codebyte/cpp |
| 91 | +#include <iostream> |
| 92 | +#include <unordered_set> |
| 93 | +
|
| 94 | +int main() { |
| 95 | + std::unordered_set<std::string> fruits = {"apple", "banana", "cherry"}; |
| 96 | +
|
| 97 | + std::cout << "Current size: " << fruits.size() << std::endl; |
| 98 | + std::cout << "Maximum size: " << fruits.max_size() << std::endl; |
| 99 | + std::cout << "Available capacity: " << fruits.max_size() - fruits.size() << std::endl; |
| 100 | +
|
| 101 | + return 0; |
| 102 | +} |
| 103 | +``` |
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