> For the complete documentation index, see [llms.txt](https://42-guide.gitbook.io/42-guide/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://42-guide.gitbook.io/42-guide/piscine-life/c02/ft_strcapitalize.md).

# ft\_strcapitalize

####

**Objective:**

The function `ft_strcapitalize` modifies a given string by capitalizing the first letter of each word while converting all other letters in the word to lowercase. A "word" is defined as a sequence of alphanumeric characters.

***

#### **Turn-in Requirements:**

* **Directory:** `ex09/`
* **File:** `ft_strcapitalize.c`
* **Allowed Functions:** None

***

#### **Prototype:**

```c
char *ft_strcapitalize(char *str);
```

***

#### **Implementation:**

```c
char	*ft_strcapitalize(char *str)
{
	int		new_word; // Flag to check if the current character is the start of a new word
	int		i;
	char	c;

	i = 0;
	new_word = 1; // The first character is always the start of a new word
	while (str[i] != '\0') // Iterate through the entire string
	{
		c = str[i];
		
		// If it's the start of a new word and the character is lowercase, convert it to uppercase
		if (new_word == 1 && c >= 'a' && c <= 'z')
			str[i] = str[i] - 32; // Convert lowercase to uppercase
		
		// If it's not a new word and the character is uppercase, convert it to lowercase
		else if (new_word == 0 && c >= 'A' && c <= 'Z')
			str[i] = str[i] + 32; // Convert uppercase to lowercase
		
		// If the character is non-alphanumeric, set new_word flag to 1 (start a new word)
		if (c < '0' || (c > '9' && c < 'A') || (c > 'Z' && c < 'a') || c > 'z')
			new_word = 1;
		else
			new_word = 0; // Otherwise, continue within the current word
		
		i++; // Move to the next character
	}
	return (str); // Return the modified string
}
```

***

#### **Explanation of the Logic:**

1. **Tracking Word Boundaries:**
   * We use the `new_word` flag to determine whether the current character is the start of a new word.
   * If a character follows a non-alphanumeric character, it's considered the first letter of a new word.
2. **Character Conversion:**
   * If `new_word == 1` and the character is lowercase (`'a' - 'z'`), it is converted to uppercase.
   * If `new_word == 0` and the character is uppercase (`'A' - 'Z'`), it is converted to lowercase.
3. **Identifying Non-Alphanumeric Characters:**
   * If the character is **not a letter or number**, it is considered a word separator, and `new_word` is set to `1`.
4. **Moving to the Next Character:**
   * The loop continues until it reaches the end of the string (`'\0'`).

***

#### **Example Usage:**

```c
#include <stdio.h>

char *ft_strcapitalize(char *str);

int main()
{
    char str1[] = "salut, comment tu vas ? 42mots quarante-deux; cinquante+et+un";
    char str2[] = "HELLO WORLD";
    char str3[] = "already Capitalized words";
    char str4[] = "";

    printf("%s\n", ft_strcapitalize(str1));
    printf("%s\n", ft_strcapitalize(str2));
    printf("%s\n", ft_strcapitalize(str3));
    printf("%s\n", ft_strcapitalize(str4));

    return 0;
}
```

#### **Expected Output:**

```php
Salut, Comment Tu Vas ? 42mots Quarante-Deux; Cinquante+Et+Un
Hello World
Already Capitalized Words
(empty string remains unchanged)
```

***

#### **Edge Cases Covered:**

* Handles words separated by spaces, punctuation, and special characters.
* Works correctly for empty strings.
* Ensures all non-initial uppercase letters are converted to lowercase.

***

#### **Complexity Analysis:**

* The function iterates through the string **once**, making it **O(n)** in time complexity, where **n** is the length of the string.
* The function modifies the input string **in place**, meaning it has **O(1)** space complexity.


---

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