[Edit] C++ Strings

content/cpp/concepts/strings/strings.md

@@ -1,44 +1,314 @@
 ---
 Title: 'Strings'
-Description: 'Strings are objects that represent sequences of characters.'
+Description: 'Strings in C++ are objects that represent sequences of characters.'
 Subjects:
   - 'Computer Science'
   - 'Game Development'
 Tags:
-  - 'Strings'
   - 'Characters'
   - 'Data Types'
+  - 'Strings'
 CatalogContent:
   - 'learn-c-plus-plus'
   - 'paths/computer-science'
 ---
 
-**Strings** are objects that represent sequences of characters. In C++, the two ways to create strings are with the `string` class or with [C-style](https://www.codecademy.com/resources/docs/c/strings) character strings.
+**Strings** are objects that represent sequences of characters. In C++, there are two ways to create strings:
 
-## String Class
+- Using the `string` class from the Standard Template Library (STL)
+- Using C-style character arrays
 
-The standard `string` class provides support for strings in C++.
+## `string` Class
+
+The standard `string` class provides robust support for string operations in C++. To use this class, include the `<string>` header:
 
 ```cpp
-std::string welcome = "Hi";
-std::string user_name = "@sonny";
-std::string message = "Good nite! 😇";
+#include <string>
+
+std::string greeting = "Hello, World!";
+std::string empty_string = "";
+std::string user_name = "@developer123";
+std::string message = "Good morning!";
 ```
 
-## C-Style Character Strings
+### Creating and Initializing Strings
+
+A string can be created and initialized in several ways:
+
+```cpp
+#include <iostream>
+#include <string>
+
+int main() {
+  // Different ways to create strings
+  std::string s1;                      // Empty string
+  std::string s2 = "C++";              // Initialization with string literal
+  std::string s3("Programming");       // Using constructor
+  std::string s4(s2);                  // Copy of another string
+  std::string s5(5, 'a');              // String with 5 'a' characters: "aaaaa"
+
+  std::cout << "s1: " << s1 << std::endl;
+  std::cout << "s2: " << s2 << std::endl;
+  std::cout << "s3: " << s3 << std::endl;
+  std::cout << "s4: " << s4 << std::endl;
+  std::cout << "s5: " << s5 << std::endl;
+
+  return 0;
+}
+```
+
+### Accessing and Modifying Strings
+
+Individual characters inside a string can be accessed and modified using indices, just like [arrays](https://www.codecademy.com/resources/docs/cpp/arrays):
+
+```cpp
+#include <iostream>
+#include <string>
+
+int main() {
+  std::string text = "Hello";
+
+  // Accessing characters
+  char first = text[0];    // 'H'
+  char last = text[4];     // 'o'
+
+  // Modifying characters
+  text[0] = 'J';           // Changes "Hello" to "Jello"
+
+  std::cout << "Modified string: " << text << std::endl;
+
+  return 0;
+}
+```
+
+### Basic String Operations
+
+The `string` class provides several useful methods for string manipulation:
+
+```cpp
+#include <iostream>
+#include <string>
+
+int main() {
+  std::string text = "C++ Programming";
+
+  // String length/size
+  std::cout << "Length: " << text.length() << std::endl;       // 15
+  std::cout << "Size: " << text.size() << std::endl;           // 15 (same as length)
+
+  // Check if empty
+  std::cout << "Is empty: " << text.empty() << std::endl;      // 0 (false)
 
-The C-style character string originated from the C language and continues to be supported within C++.
+  // Substring extraction
+  std::string sub = text.substr(0, 3);                         // "C++"
+  std::cout << "Substring: " << sub << std::endl;
+
+  // Find position of a substring
+  size_t position = text.find("Programming");
+  if (position != std::string::npos) {
+    std::cout << "Found at position: " << position << std::endl; // 4
+  }
+
+  return 0;
+}
+```
 
-In C, the string is actually an array of characters, followed by a `null` character `'\0'`.
+### String Concatenation
+
+Strings can be joined with the `+` operator or the `.append()` method:
+
+```cpp
+#include <iostream>
+#include <string>
+
+int main() {
+  std::string first_name = "Ada";
+  std::string last_name = "Lovelace";
+
+  // Using + operator
+  std::string full_name = first_name + " " + last_name;
+
+  // Using .append() method
+  std::string greeting = "Hello, ";
+  greeting.append(first_name);
+
+  // Using += operator
+  std::string message = "Welcome ";
+  message += "to C++!";
+
+  std::cout << full_name << std::endl;
+  std::cout << greeting << std::endl;
+  std::cout << message << std::endl;
+
+  return 0;
+}
+```
+
+This example results in:
+
+```shell
+Ada Lovelace
+Hello, Ada
+Welcome to C++!
+```
+
+## C-Style Character Strings
+
+C-style strings are character arrays that originated from the [C](https://www.codecademy.com/resources/docs/c) language and continue to be supported in C++. In C, a string represents an array of characters, terminated by a `null` character `'\0'`.
 
 ```cpp
 char message[] = "Howdy";
 ```
 
-So here's the memory presentation:
+The memory representation of this C-style string looks like this:
 
 ```shell
 Character |   'H'    'o'    'w'    'd'    'y'   '\0'
 Index     |    0      1      2      3      4      5
 Address   |  23451  23452  23453  23454  23455  23456
 ```
+
+### Creating C-Style Strings
+
+C-style strings can be created in several ways:
+
+```cpp
+#include <iostream>
+
+int main() {
+  // Different ways to create C-style strings
+  char str1[] = "C++";                           // Automatic size calculation
+  char str2[4] = "C++";                          // Explicitly specify size (including null character)
+  char str3[] = {'C', '+', '+', '\0'};           // Character by character with null terminator
+  char str4[100] = "Programming";                // With extra space allocation
+
+  std::cout << "str1: " << str1 << std::endl;
+  std::cout << "str2: " << str2 << std::endl;
+  std::cout << "str3: " << str3 << std::endl;
+  std::cout << "str4: " << str4 << std::endl;
+
+  return 0;
+}
+```
+
+### Working with C-Style Strings
+
+C-style strings require the `<cstring>` header for string manipulation operations:
+
+```cpp
+#include <iostream>
+#include <cstring>
+
+int main() {
+  char str1[20] = "Hello";
+  char str2[20] = "World";
+  char result[40];
+
+  // String length
+  std::cout << "Length of str1: " << strlen(str1) << std::endl;
+
+  // String copy
+  strcpy(result, str1);
+  std::cout << "After strcpy: " << result << std::endl;
+
+  // String concatenation
+  strcat(result, " ");
+  strcat(result, str2);
+  std::cout << "Concatenated string: " << result << std::endl;
+
+  // String comparison
+  int comparison = strcmp(str1, str2);
+  if (comparison < 0) {
+    std::cout << "str1 is less than str2" << std::endl;
+  } else if (comparison > 0) {
+    std::cout << "str1 is greater than str2" << std::endl;
+  } else {
+    std::cout << "str1 equals str2" << std::endl;
+  }
+
+  return 0;
+}
+```
+
+The output looks like this:
+
+```shell
+Length of str1: 5
+After strcpy: Hello
+Concatenated string: Hello World
+str1 is less than str2
+```
+
+## `string` Class vs. C-Style Strings
+
+Here are some key differences between the two string types:
+
+| Feature           | `string` Class            | C-Style Strings           |
+| ----------------- | ------------------------- | ------------------------- |
+| Memory management | Automatic                 | Manual                    |
+| Bounds checking   | Yes                       | No                        |
+| Size              | Dynamic (can grow/shrink) | Fixed at declaration      |
+| Null termination  | Handled automatically     | Must be managed manually  |
+| Concatenation     | Using `+` operator        | Using `strcat()`          |
+| Comparison        | Using `==`, `!=`, etc.    | Using `strcmp()`          |
+| Character access  | Using `[]` or `at()`      | Using `[]`                |
+| Required header   | `<string>`                | `<cstring>`               |
+| Memory safety     | Safe                      | Prone to buffer overflows |
+
+> **Note:** The `string` class is generally preferred in modern C++ for its safety and convenience features.
+
+## Converting Between String Types
+
+You can convert between `std::string` and C-style strings:
+
+```cpp
+#include <iostream>
+#include <string>
+#include <cstring>
+
+int main() {
+  // C-style string to std::string
+  char cstr[] = "Hello C++";
+  std::string str1(cstr);
+
+  // std::string to C-style string
+  std::string str2 = "C++ Programming";
+  const char* cstr2 = str2.c_str();  // Get a C-style string pointer
+
+  std::cout << "str1: " << str1 << std::endl;
+  std::cout << "cstr2: " << cstr2 << std::endl;
+
+  return 0;
+}
+```
+
+## Frequently Asked Questions
+
+### 1. What's the difference between `length()` and `size()` for strings?
+
+In C++, the [`length()`](https://www.codecademy.com/resources/docs/cpp/strings/length) and [`size()`](https://www.codecademy.com/resources/docs/cpp/strings/size) methods of the `string` class are functionally identical. Both return the number of characters in the string. The dual naming is historical - `size()` is consistent with other STL containers, while `length()` is more intuitive for strings.
+
+```cpp
+std::string text = "Hello";
+std::cout << text.length(); // Returns 5
+std::cout << text.size();   // Also returns 5
+```
+
+### 2. Why should I use string class instead of C-style strings?
+
+The `string` class provides several advantages over C-style strings:
+
+- **Memory management:** Automatically handles allocation and deallocation
+- **Safety:** Protects against buffer overflows
+- **Functionality:** Provides built-in methods for common operations
+- **Flexibility:** Can dynamically grow and shrink as needed
+
+C-style strings require manual memory management and are prone to errors like buffer overflows.
+
+### 3. How do I convert a number to a string in C++?
+
+The simplest way to convert a number to a string in modern C++ is to use the `std::to_string()` function:
+
+For example: `std::to_string(42)` returns the string `"42"`.
+
+For converting a string to a number, you can use functions like `std::stoi()` (string to int), `std::stof()` (string to float), etc. For example, `std::stoi("42")` returns the integer `42`.