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. cout << str.substr(7, 8) << endl; c. string::size_type ind = str.find('f'); string s = str.substr(ind + 4, 9); cout << s << endl; d. cout << str.insert(11, "best ") << endl; e. str.erase(16, 14); str.insert(16, "to study for the exam?"); cout << str << endl;

Short answer

a. 30 b. the time c. the part d. Now is the best time for the party! e. Now is the be to study for the exam?

Step-by-step solution

Analyze Part (a)

The method `str.size()` returns the number of characters in the string `str`. In this case, `str` is "Now is the time for the party!", which has 30 characters. Therefore, the output of `cout << str.size() << endl;` will be `30`.

Evaluate Part (b)

The method `str.substr(7, 8)` returns a substring starting at index 7 with a length of 8 characters. In the string "Now is the time for the party!", index 7 is the character 't'. Counting 8 characters from there, the substring is "the time". Therefore, the output will be `the time`.

Determine Output for Part (c)

First, `str.find('f')` finds the index of the first occurrence of the character 'f', which is at index 16. Then, `str.substr(ind + 4, 9)` starts from index 20 ('h') and extracts 9 characters, yielding the substring "the part". This is stored in string `s`, and `cout << s << endl;` outputs `the part`.

Perform Part (d)

The `str.insert(11, "best ")` inserts the string "best " at index 11 in "Now is the time for the party!", resulting in "Now is the best time for the party!". The statement `cout << str.insert(11, "best ") << endl;` outputs `Now is the best time for the party!`.

Execute Part (e)

`str.erase(16, 14)` removes 14 characters starting from index 16, modifying the string to "Now is the be party!". Then, `str.insert(16, "to study for the exam?")` inserts "to study for the exam?" at index 16, resulting in the final string "Now is the be to study for the exam?". The statement `cout << str << endl;` outputs `Now is the be to study for the exam?`.

Key concepts

C++ substr function

The `substr` function in C++ is an essential string manipulation tool that allows you to extract a portion of a string. Using `substr`, you can specify two parameters: the starting position and the length of the substring that you wish to extract. For example, `str.substr(7, 8)` gives you a substring starting at the 7th index and takes the next 8 characters. In our string "Now is the time for the party!", this operation extracts "the time" as it begins at the character 't'.
This function is particularly powerful because:

• It allows for dynamic handling of strings based on computed values, such as indices found through other string operations.
• If the length argument exceeds the string's remaining length, it simply extracts until the string's end, preventing errors.

By mastering the `substr` function, you'll be able to manage and manipulate string data effectively in your C++ programs.

C++ insert function

The `insert` function in C++ is used to add additional text into a string at a specified index. This is highly useful when you need to insert extra information within an existing sentence structure. Consider the function call `str.insert(11, "best ")`. Here, the word "best " is inserted at the 11th position of the string "Now is the time for the party!", effectively modifying it to "Now is the best time for the party!".
The key elements of the `insert` function include:

• Index Position: Dictates where in the string the insertion will occur, which allows for precise control over string modification.
• String to Insert: Specifies what text will be inserted, enabling dynamic content addition.

Understanding `insert` allows for flexible content creation in software systems or during string-formatting tasks within C++.

C++ erase function

The `erase` function in C++ is designed to remove a segment of a string, starting at a specified position and continuing for a defined number of characters. This can be quite useful if you need to delete unwanted parts from a string to achieve the desired output.
For instance, `str.erase(16, 14)` removes a section starting at the 16th character with 14 characters long, effectively cutting "the time for the" out from "Now is the time for the party!", making it "Now is the be party!".
Important points regarding the `erase` function include:

• Starting Index: Determines the initial point of deletion.
• Length: Specifies how many characters to remove from the string.

When correctly utilized, the `erase` function provides efficient string adjustment capabilities, allowing you to tailor strings to your exact specifications.

C++ find function

The `find` function in C++ is used to locate the index of the first occurrence of a substring or character within a string. This is immensely helpful when you need to determine where certain characters or sequences are in your text. For example, the call `str.find('f')` searches for the first occurrence of the character 'f' in the string "Now is the time for the party!", which is at index 16.
The characteristics and utility of the `find` function include:

• Returns the index of the first match found, providing clarity about the string's composition.
• If the substring or character is not found, it returns `string::npos`, a constant representing a non-existent position within the string.

This function is an invaluable tool when processing text where position and context are relevant, such as parsing or analyzing data contained within strings.