Question

Consider the following statement: string str \(=\) "Now is the time for the party!"; What is the output of the following statements? (Assume that all parts are independent of each other.) a. cout \(<<\) str.size ()\(<<\) endl b. \(\operatorname{cout}<<\operatorname{str} . \operatorname{substr}(7,8)<<\operatorname{end} 1\) c. string: : size_type ind \(=\operatorname{str} .\) find \((\text { 'f } ')\) string \(s=s t r .\) substr \((i n d+4,9)\) cout \(<<\mathrm{s}<<\) endl d. cout \(<<\) str.insert \((11, \text { "best } ")<<\) endl e. str.erase (16,14) str.insert \((16,\) "to study for the exam? "); cout \(<<\) str \(<<\) endl

Short answer

a. 29 b. "the time" c. "the party" d. "Now is the best time for the party!" e. "Now is the time to study for the exam? "

Step-by-step solution

Calculate string size for statement a

The function `str.size()` returns the number of characters in the string "Now is the time for the party!" including spaces and punctuation. String: "Now is the time for the party!" The string has 29 characters. Thus, the statement `cout << str.size() << endl` will output `29`.

Extract substring for statement b

The `str.substr(7, 8)` function extracts a substring starting at index 7 and of length 8 characters from the string. Original String: "Now is the time for the party!" Starting at index 7, the substring is "the time". The statement `cout << str.substr(7,8) << endl` will output "the time".

Find and extract substring for statement c

First, we find the index of the character 'f' in the string using `str.find('f')`, which returns 16. Next, the segment `str.substr(ind+4, 9)` extracts a substring starting from index `16 + 4 = 20` with length 9. The substring starting at index 20 is "the party". Thus, the statement will output "the party".

Insert a substring for statement d

The `str.insert(11, "best ")` method inserts the substring "best " starting at index 11. Original String: "Now is the time for the party!" String after insertion: "Now is the best time for the party!" The statement `cout << str.insert(11, "best ") << endl` will output "Now is the best time for the party!".

Erase and insert new substring for statement e

First, `str.erase(16, 14)` will remove 14 characters starting from index 16. String after erase: "Now is the time to study!" Then, `str.insert(16, "to study for the exam? ")` inserts the new phrase. Final string: "Now is the time to study for the exam? " Thus, the statement will output "Now is the time to study for the exam? "

Key concepts

C++ Programming

C++ is a powerful programming language that provides a robust framework for software development. It supports object-oriented, procedural, and even functional programming styles, which makes it versatile for solving varied types of problems. In C++, strings are a useful way to handle and manipulate text data. They come into play especially in applications needing dynamic manipulation of text, such as text processing and user interaction applications.
In C++, strings are objects of the `std::string` class, which is part of the C++ Standard Library. This class offers a wide range of functions to perform different operations on strings, such as appending, searching, replacing, and comparing substrings. This functionality is integral in creating efficient, readable, and maintainable code.
Understanding string operations, like we explore in the following sections, is essential for becoming proficient in C++ programming. Let's dive deeper into some specific functions that C++ provides for handling strings.

string functions

String functions in C++ are built-in operations that allow developers to manipulate string data effectively. These functions simplify tasks that, if done manually, would require considerable effort and complexity.
Some key string functions include:

• `size()` or `length()`: These functions return the number of characters in a string, which can include letters, numbers, symbols, and spaces.
• `substr(pos, len)`: This function extracts a substring from a specified starting position 'pos' with a specified length 'len'. It's particularly useful when working with parts of strings.
• `find(str)`: This returns the position where a specified substring or character first occurs in the main string. It's a handy tool for searching within a string.
• `insert(pos, str)`: Allows for inserting a string at a specific position, altering the original string.
• `erase(pos, len)`: This deletes part of the string starting at the given position 'pos' and extends for 'len' characters.

Understanding these functions and how to apply them helps in coding more dynamic and flexible applications.

substring extraction

Substring extraction in C++ is a method used to grab specific parts of a string for processing or reference. This process is performed using the `substr` function from the `std::string` class. It is exceptionally useful in scenarios where you need to isolate a portion of the string for analysis or modification.
To extract a substring, you use `substr(startingIndex, length)`. Here, `startingIndex` is the zero-based position where the substring begins, and `length` is how many characters you wish to include in the substring.
For example, if you have the string `"Hello, World!"` and you want to extract just "World", you would call `string.substr(7, 5)` because "World" starts at index 7 and is 5 characters long. This functionality is widely used across software that requires parsing and processing of user data or text files.

string insertion

String insertion is the act of adding a sequence of characters into a string at a specified position. In C++, this can be easily accomplished using the `insert` method provided by the `std::string` class.
To use this method, you call `str.insert(position, substring)`, where `position` indicates the index in the original string where the new text should appear, and `substring` is the actual sequence of characters you want to insert.
Consider the example of inserting "best " into the string "Now is the time", resulting in "Now is the best time". By calling `str.insert(8, "best ")`, you tell the program to start inserting the substring "best " at index 8 of the original string, shifting the remaining characters to form the complete sentence. This operation is crucial when enhancing string data, accommodating new information, or simply adjusting content structure dynamically.

string erase

Erasing part of a string in C++ is a straightforward task thanks to the `erase` method in the `std::string` class. This method allows for the removal of segments of a string, which can be useful for simplifying a string or removing unwanted data.
The syntax for erasing is `str.erase(startingIndex, length)`, where `startingIndex` is the position to begin deletion, and `length` is the number of characters to remove.
For instance, if you have the string "I love programming in C++" and you want to remove "programming", you would use `str.erase(7, 11)` since "programming" starts at index 7 and has 11 characters. After the erase operation, the string would become "I love in C++". Such operations are key in real-time applications, data cleaning, and manipulation where keeping strings concise and relevant is necessary.