9: Custom Data Types

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Questions and Answers

What is the primary reason for creating custom data types in C++?

To represent data types that are not built-in (correct)

To make the code more complex

To avoid using built-in types

To increase execution speed

C++ has a built-in type specifically for rational numbers.

False

What are the two components of a rational number as defined in the content?

n and d

To perform calculations with rational numbers, we create a custom type called ___.

rational Signup and view all the answers

Match the following C++ operations with their relevance to the custom type 'rational':

Input = std::cout >> r Calculation = rational t = r + s Output = std::cout << t Declaration = rational r; Signup and view all the answers

What is the result of the function call `sum({-1, 4, 6, 7}, 0)`?

16 Signup and view all the answers

The iterative solution for summing elements of a vector is less efficient than the recursive solution.

False Signup and view all the answers

What is the base case for the recursive function when summing elements of a vector?

from >= int(v.size()) Signup and view all the answers

In the second variant of the sum function, if `from` equals `to`, the function returns the value of ___ at that index.

v.at(from) Signup and view all the answers

Which method applies a 'divide and conquer' strategy to summing elements of a vector?

sum(const std::vector& v, int from, int to) Signup and view all the answers

The function `sum({7})` returns 0.

False Signup and view all the answers

What is the value returned by the function when called with an empty vector, `sum({})`?

0 Signup and view all the answers

To find the middle index in the recursive sum function, the formula used is `middle = (from + to) / ___`.

2 Signup and view all the answers

Match each function variant to its characteristics:

sum(const std::vector& v, int from) = Single index recursion sum(const std::vector& v, int from, int to) = Divide and conquer strategy sum({}) = Returns 0 sum({7}) = Returns single element Signup and view all the answers

Identify a key difference between iterative and recursive solutions in programming.

Recursion uses function calls and stack, while iteration uses loops. Signup and view all the answers

Which of the following statements about 'Decrease and Conquer' is true?

It makes one recursive call on the remainder. Signup and view all the answers

The Fibonacci sequence starts with the numbers 0 and 1.

True Signup and view all the answers

What is the time complexity implication of naive Fibonacci calculation through recursion?

Exponential time complexity due to recomputing values. Signup and view all the answers

The Fibonacci function in C++ makes recursive calls to and .

fib(n-1) and fib(n-2) Signup and view all the answers

Match the Fibonacci numbers with their corresponding index:

F0 = 0 F1 = 1 F2 = 1 F3 = 2 Signup and view all the answers

What is a key property of 'Divide and Conquer' algorithms?

Halve the elements for processing. Signup and view all the answers

An iterative Fibonacci algorithm computes each Fibonacci number multiple times.

False Signup and view all the answers

How many times is F48 computed in the naive recursive Fibonacci implementation?

The method for calculating Fibonacci numbers that uses a single recursive call is called _______.

Divide and Conquer Signup and view all the answers

Which of the following best describes the recursion depth in 'Decrease and Conquer' algorithms?

It is generally less than in 'Divide and Conquer' algorithms. Signup and view all the answers

What is the correct syntax to create an object of the struct type 'str name' with initial values?

str name obj1 = {3, true, 4}; Signup and view all the answers

A struct does not require a semicolon at the end of its definition.

False Signup and view all the answers

What happens to fundamental types of members in a struct during default initialization?

They are uninitialized. Signup and view all the answers

To access the member 'mem1' of an object named 'obj1', you write ______.

obj1.mem1 Signup and view all the answers

Match the following struct names with their use case:

struct str name = Define a custom data type struct candidate = Store participant information obj1 = An instance of str name obj2 = An initialized object with values Signup and view all the answers

Which of the following statements about member initialization in a struct is true?

Member values can be accessed directly using their names. Signup and view all the answers

The assignment operator '=' is automatically created for a struct in C++.

True Signup and view all the answers

What is the purpose of overloading operators for custom data types in C++?

To define how operators behave for the custom type. Signup and view all the answers

Study Notes

Introduction to Computer Science

Course code: 252-0032, 252-0047, 252-0058
Authors: Manuela Fischer and Felix Friedrich
Department: Computer Science, ETH Zurich
Semester: Fall 2024

Custom Data Types

Students learn to create their own data types if built-in types are insufficient.
Example use case: performing calculations with rational numbers (n/d where n and d are integers).
C++ does not have a built-in rational type.

Struct Declaration

Defining a new type: use a struct
Struct name becomes a new type
Inside curly braces, declare member variables (of any fundamental or user-defined type)
Member variable names and types are defined in a struct
Example: struct rational { int n; int d; }; (numerator n, denominator d)

Struct Initialization

Default initialization: uses default values for member variables (undefined values for fundamental types; no initialization)
Member-wise assignment from another struct: r=s; copies values from s into r
Aggregate initialization: defines initial values for members using a list in the declaration rational s = {5, 2}; (first =n, second =d)

Structs as Function Arguments

Structs can be used as function arguments
Example function for adding two rational numbers:

rational add(rational a, rational b) {
    rational result;
    result.n = a.n * b.d + a.d * b.n;
    result.d = a.d * b.d;
    return result;
}

Function and Operator Overloading

Function overloading: defining multiple functions with the same name but different parameters (e.g., sq(double x), sq(int x))
Operator overloading: defining functions for operators like +, -, *, /, == for user-defined types (e.g., rational).
Operator + for rational:

rational operator+(rational a, rational b) {
 rational result;
 ...
 return result; 
}

Example of operator +=:

rational& operator+=(rational& a, rational b){
 a= a + b;
 return a;
}

Arithmetic operators

Overloading operators (+, -, *, /) for rational numbers
Allowing expressions like r + s.
Unary minus operator:

rational operator-(rational a) {
  a.n = -a.n;
  return a;
}

Arithmetic Assignment

Overloading assignment operators (+=, -=, *=, /=): allowing expressions like r+=s.
Ensuring that assignment operators return a reference to the left-hand side for chaining, to allow for expressions like r += s;

Comparison Operators

Defining comparison operators (==,!=, <, >, <=, >=) for rational numbers to allow comparisons.
Example bool operator==(rational a, rational b) allowing expressions like r==s.

Input and Output Operators

Overloading input operator (>>):
reading a rational number from input stream (e.g., std::cin):

std::istream& operator >> (std::istream& in, rational& r) {
    char c;
    in >> r.n >> c >> r.d; // read n '/' and d
    return in;
}

Overloading output operator (<<): writing a rational number to output stream (e.g., std::cout)

std::ostream& operator << (std::ostream& out, rational r) {
    return out << r.n<< "/" << r.d;
}

Using std::cout and std::cin for input and output

Guarantee Invariants

Invariants: ensure member variables respect constraints (e.g., denominator (d) is not zero).
Tools needed for this feature not yet included in the study notes.

Studying That Suits You

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Description

This quiz covers the creation and implementation of custom data types in C++, focusing on struct declarations and initializations. Understand how to define and use structures to manage complex data effectively. Test your knowledge on struct member variables and their initial setups.

9: Custom Data Types

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Podcast

Questions and Answers

What is the primary reason for creating custom data types in C++?

C++ has a built-in type specifically for rational numbers.

What are the two components of a rational number as defined in the content?

To perform calculations with rational numbers, we create a custom type called ___.

Match the following C++ operations with their relevance to the custom type 'rational':

What is the result of the function call sum({-1, 4, 6, 7}, 0)?

The iterative solution for summing elements of a vector is less efficient than the recursive solution.

What is the base case for the recursive function when summing elements of a vector?

In the second variant of the sum function, if from equals to, the function returns the value of ___ at that index.

Which method applies a 'divide and conquer' strategy to summing elements of a vector?

The function sum({7}) returns 0.

What is the value returned by the function when called with an empty vector, sum({})?

To find the middle index in the recursive sum function, the formula used is middle = (from + to) / ___.

Match each function variant to its characteristics:

Identify a key difference between iterative and recursive solutions in programming.

Which of the following statements about 'Decrease and Conquer' is true?

The Fibonacci sequence starts with the numbers 0 and 1.

What is the time complexity implication of naive Fibonacci calculation through recursion?

The Fibonacci function in C++ makes recursive calls to ______ and ______.

Match the Fibonacci numbers with their corresponding index:

What is a key property of 'Divide and Conquer' algorithms?

An iterative Fibonacci algorithm computes each Fibonacci number multiple times.

How many times is F48 computed in the naive recursive Fibonacci implementation?

The method for calculating Fibonacci numbers that uses a single recursive call is called _______.

Which of the following best describes the recursion depth in 'Decrease and Conquer' algorithms?

What is the correct syntax to create an object of the struct type 'str name' with initial values?

A struct does not require a semicolon at the end of its definition.

What happens to fundamental types of members in a struct during default initialization?

To access the member 'mem1' of an object named 'obj1', you write ______.

Match the following struct names with their use case:

Which of the following statements about member initialization in a struct is true?

The assignment operator '=' is automatically created for a struct in C++.

What is the purpose of overloading operators for custom data types in C++?

Study Notes

Introduction to Computer Science

Custom Data Types

Struct Declaration

Struct Initialization

Structs as Function Arguments

Function and Operator Overloading

Arithmetic operators

Arithmetic Assignment

Comparison Operators

Input and Output Operators

Guarantee Invariants

Studying That Suits You

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What is the result of the function call `sum({-1, 4, 6, 7}, 0)`?

In the second variant of the sum function, if `from` equals `to`, the function returns the value of ___ at that index.

The function `sum({7})` returns 0.

What is the value returned by the function when called with an empty vector, `sum({})`?

To find the middle index in the recursive sum function, the formula used is `middle = (from + to) / ___`.

The Fibonacci function in C++ makes recursive calls to and .