시스템 프롬프트 실습

# Python Function to Check for Duplicate Characters in a String

```python
def has_duplicate_characters(string):
    """
    Checks if a string contains any duplicate characters.

    Args:
        string (str): The input string to check for duplicates

    Returns:
        bool: True if the string has duplicate characters, False otherwise
    """
    # Create an empty set to keep track of seen characters
    seen_chars = set()

    # Iterate through each character in the string
    for char in string:
        # If we've seen this character before, there's a duplicate
        if char in seen_chars:
            return True
        # Otherwise, add it to our set of seen characters
        seen_chars.add(char)

    # If we made it through the entire string without finding duplicates
    return False

# Example usage
if __name__ == "__main__":
    test_cases = [
        "abcde",        # No duplicates
        "hello",        # Duplicate 'l'
        "python",       # No duplicates
        "programming",  # Duplicate 'r', 'g', 'm'
        "",             # Empty string
        "aaa"           # Multiple duplicates
    ]

    for test in test_cases:
        result = has_duplicate_characters(test)
        print(f"'{test}' has duplicate characters: {result}")
```

This function:
1. Uses a set to track characters we've seen while iterating
2. Returns True as soon as it finds a duplicate
3. Returns False if it gets through the whole string
4. Has O(n) time complexity where n is the length of the string