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Chapter 18: Problem 12

Write a program that inputs a string and prints the string backward. Convert all uppercase characters to lowercase and all lowercase characters to uppercase.

Short Answer

Expert verified
To solve this, reverse the input string and use the `swapcase()` method, then print the modified string.

Step by step solution

01

Obtain Input

Start by writing a program that prompts the user for a string input. This can be done using a function like `input()` in Python.
02

Reverse the String

Once the input is obtained, the next step is to reverse the string. You may use slicing with a step of -1 in Python (e.g., `reversed_string = input_string[::-1]`).
03

Swap Case

With the reversed string, the next step is to swap the case of each character. In Python, this can be done using the `swapcase()` method on the string (e.g., `swapped_case_string = reversed_string.swapcase()`).
04

Print the Altered String

After reversing the string and swapping the cases, you can print the final result using the `print()` function.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

String Reversal
String reversal is a common operation in programming where the order of characters in a string is inverted. In C++, string reversal can be performed by iterating through the string from the end to the beginning, and appending each character to a new string.

This approach can be realized using a for-loop or the built-in `std::reverse` function from the `` header file. For instance, if you have a string `std::string original`, you can reverse it by doing `std::reverse(original.begin(), original.end());`. This manipulates the original string in place, making it reversed when the operation is complete.

In the context of the exercise, string reversal is the second step after inputting the string, and it sets up the stage for the next operation which is character case conversion.
Character Case Conversion
Character case conversion in C++ is about changing each letter in a string from uppercase to lowercase or vice versa. There are multiple ways to accomplish this, including using ASCII values, or the `toupper` and `tolower` functions available in the `` header.

For each character in the string, check if it is upper or lowercase using `isupper` or `islower`, and subsequently convert it using `toupper` or `tolower`. This produces the result needed for the exercise, where the reversal of the string is immediately followed by case conversion.

However, unlike Python's `swapcase()`, C++ does not have a direct standard library function that changes the case of each character, therefore, it will require a loop that processes each character individually.
String Input and Output
Handling string input and output is fundamental in many C++ programs. Input can be obtained from the user through the console using `std::cin`, or from a file using file streams. To read a string from the console, you simply use `std::cin >> variable;` or `std::getline(std::cin, variable);` for input with spaces.

Once you have processed the string as per the requirements of an exercise or application's logic, you can output it using `std::cout`. Thus, `std::cout << variable;` will display the result on the screen. In our exercise, after performing the reversal and case conversion, the final step is to output the transformed string which is done through this method.
C++ String Handling
C++ provides various tools and functions for string handling, encapsulated within the `std::string` class found in the `` header. This class offers an array of methods for string manipulation, including appending (`+=`), comparison (`==`, `!=`, `<`, `>`), searching (`find`), and modifying (`replace`, `erase`).

For the exercise discussed, basic string operations are employed. However, understanding the full capability of `std::string` is important. It can simplify many complex tasks involving strings, such as finding substrings, replacing characters, or splitting strings based on a delimiter.

Utilizing the `std::string` class effectively can significantly reduce the amount of code needed for string manipulation tasks in C++ and make code more readable and manageable.

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Most popular questions from this chapter

State which of the following statements are true and which are false. If a statement is \(f a l\) se, explain why. a) strings are always null terminated. b) Class string member function max_size returns the maximum size for a string. c) Class string member function at can throw an out_of_range exception. d) Class string member function begin returns an iterator.

Some information on the Internet may be encrypted with a simple algorithm known as "rot13," which rotates each character by 13 positions in the alphabet. Thus, 'a' corresponds to 'n', and'x' corresponds to 'k'. rot13 is an example of symmetric key encryption. With symmetric key encryption, both the encrypter and decrypter use the same key. a) Write a program that encrypts a message using rot13. b) Write a program that decrypts the scrambled message using 13 as the key. c) After writing the programs of part (a) and part (b), briefly answer the following question: If you did not know the key for part (b), how difficult do you think it would be to break the code? What if you had access to substantial computing power (e.g., supercomputers)? In Exercise 18.25 we ask you to write a program to accomplish this.

Write a program that plays the game of Hangman. The program should pick a word (which is either coded directly into the program or read from a text file) and display the following: Guess the word: \(x x x x x x\) Each \(x\) represents a letter. The user tries to guess the letters in the word. The appropriate response yes or no should be displayed after each guess. After each incorrect guess, display the diagram with another body part filled. After seven incorrect guesses, the user should be hanged. The display should look as follows:

Write a program that separately inputs a first name and a last name and concatenates the two into a new string. Show two techniques for accomplishing this task.

Write a program that counts the total number of vowels in a sentence. Output the frequency of each vowel.
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