joj 2653 不同的数 从2*n中找出不相同的两个数

### Python Join Function Usage and Examples In Python, the `str.join()` method is a string operation that returns a string in which the elements of sequence have been joined by a specified separator. The syntax for this function is as follows: ```python 'connector'.join(iterable) ``` The parameter `iterable` must be a series of strings; otherwise, a `TypeError` will occur unless all items can be converted into strings implicitly. For instance, joining words with spaces or creating comma-separated values are common use cases: ```python words = ["hello", "world"] print(' '.join(words)) # hello world csv_elements = ['apple', 'banana', 'cherry'] print(','.join(csv_elements)) # apple,banana,cherry ``` When working with file paths where slashes need to separate directory names, one might also utilize join: ```python path_parts = ['folder1', 'subfolder2', 'file.txt'] print('/'.join(path_parts)) # folder1/subfolder2/file.txt ``` To concatenate multiple lines within a single string while ensuring each part appears on its own line, newline characters serve well as separators: ```python lines = ["First line", "Second line", "Third line"] multi_line_string = '\n'.join(lines) print(multi_line_string) # First line # Second line # Third line ``` It's important to note that only string types should reside inside the iterable passed to `.join()`. If integers exist among these elements, they require conversion first using methods like list comprehension combined with str(): ```python numbers = [1, 2, 3] string_numbers = '-'.join([str(num) for num in numbers]) print(string_numbers) # 1-2-3 ``` --related questions-- 1. How does the performance of `str.join()` compare against other concatenation techniques? 2. What exceptions may arise when improperly utilizing `str.join()`? 3. Can you provide scenarios beyond those mentioned here where `str.join()` proves particularly useful? 4. Is there any difference between `''.join(list)` versus directly adding strings together via `+` operator concerning memory allocation?