Question

Write a program that inputs a line of text, tokenizes the line with function strtok and outputs the tokens in reverse order.

Short answer

Input text, tokenize with `strtok`, store tokens, reverse them, then output.

Step-by-step solution

Input the Text

Start by writing a program that allows the user to input a line of text. This can often be done using standard input functions in the programming language of your choice (e.g., `scanf` in C, `input` in Python). Store the input in a suitable variable, such as a string.

Tokenize the Text

Use the `strtok` function to split the input text into individual tokens. The function requires the text to tokenize and delimiter(s) as parameters (commonly a space " " for splitting words). Call `strtok` to get the first token and use a loop to continue getting the next tokens until `strtok` returns `NULL` which indicates there are no more tokens.

Store Tokens in a List

As you extract each token with `strtok`, append it to a list (or an array) so that you can easily store all tokens. This will allow you to access and manipulate the tokens easily later.

Reverse the Order of Tokens

Once all tokens are stored in a list, reverse the order of this list. You can either use a language-provided function to reverse the list, like `reverse()` in Python or manually swap elements if required in languages that do not have such utilities.

Output the Tokens

After reversing the list of tokens, iterate through the list and output each token. Ensure that the tokens are printed in a single line, separated by spaces, to match the original layout reformatted in reverse order.

Key concepts

strtok function

When working with strings in C++, the `strtok` function is invaluable for breaking strings into smaller, more manageable pieces known as tokens. This is particularly useful when you have a line of text and you need to segment it into words or distinct parts. To begin using `strtok`, you must specify the string you want to tokenize and the delimiters. Delimiters are the characters that will determine where the string splits. Common delimiters include spaces, commas, or periods.

• The function returns the first token found.
• Subsequent calls to `strtok`, using `NULL` as the first argument, process further tokens from the same initial string.
• It keeps track of its progress internally, returning NULL when there are no more tokens to retrieve.

By understanding how `strtok` functions, programmers can effectively divide input text into useful segments for further processing.

text processing

Text processing refers to reading, processing, and transforming text data effectively and efficiently. In programming, this requires understanding how to manipulate strings to extract meaningful information. In the context of the exercise, text processing begins by accepting user input and continues through several steps:

• Input is usually handled through standard functions, such as `cin` in C++.
• Next, the text undergoes tokenization, which involves dividing it into tokens using `strtok`.
• Finally, the tokens are collected and potentially altered or analyzed to fit the requirements.

Effective text processing requires careful handling of input and output, ensuring that data is segmented and accessed as needed for your program’s goals.

input manipulation

Input manipulation refers to the ways in which data or text received from users is modified or processed to suit the needs of a program. This could be as simple as stripping unwanted characters or as complex as restructuring data for analysis.

• Initially, user input must be captured accurately, typically via `cin` or similar functions.
• Prior to manipulation, consider validating the input to ensure it meets expected criteria.
• During manipulation, tokens could be stored, counted, or analyzed to glean further insights or to prepare them for output.

Through input manipulation, you ensure the data is in the optimal form for whatever task your program is performing. This could mean correctly ordering information or preparing it for further computation.

reverse order output

Sometimes it's necessary to alter the sequence of data, such as presenting text in reverse. This is particularly common in tasks where analysis of data structure is required. Once tokens are extracted from the text line and stored in a list or an array, reversing their order is the next logical step. This can usually be accomplished with simple commands, such as the `reverse()` function, or by manually swapping elements in languages lacking native support.

• Consider each element's new position in the list after reversing.
• Ensure that any printing or further processing respects this reversed order to retain accuracy.
• Output should format tokens in a readable manner, maintaining any necessary spacing or punctuation to match the original sentence's style, albeit in reverse order.

Applying reverse order output can significantly change the viewer's understanding or the usability of the processed data.