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 (B)

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 ___.

<p>rational</p> Signup and view all the answers

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

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

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

<p>16 (D)</p> Signup and view all the answers

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

<p>False (B)</p> Signup and view all the answers

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

<p>from &gt;= int(v.size())</p> 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.

<p>v.at(from)</p> Signup and view all the answers

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

<p>sum(const std::vector&amp; v, int from, int to) (C)</p> Signup and view all the answers

The function sum({7}) returns 0.

<p>False (B)</p> Signup and view all the answers

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

<p>0</p> Signup and view all the answers

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

<p>2</p> Signup and view all the answers

Match each function variant to its characteristics:

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

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

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

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

<p>It makes one recursive call on the remainder. (C)</p> Signup and view all the answers

The Fibonacci sequence starts with the numbers 0 and 1.

<p>True (A)</p> Signup and view all the answers

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

<p>Exponential time complexity due to recomputing values.</p> Signup and view all the answers

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

<p>fib(n-1) and fib(n-2)</p> Signup and view all the answers

Match the Fibonacci numbers with their corresponding index:

<p>F0 = 0 F1 = 1 F2 = 1 F3 = 2</p> Signup and view all the answers

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

<p>Halve the elements for processing. (A)</p> Signup and view all the answers

An iterative Fibonacci algorithm computes each Fibonacci number multiple times.

<p>False (B)</p> Signup and view all the answers

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

<p>2 times</p> Signup and view all the answers

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

<p>Divide and Conquer</p> Signup and view all the answers

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

<p>It is generally less than in 'Divide and Conquer' algorithms. (C)</p> Signup and view all the answers

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

<p>str name obj1 = {3, true, 4}; (B)</p> Signup and view all the answers

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

<p>False (B)</p> Signup and view all the answers

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

<p>They are uninitialized.</p> Signup and view all the answers

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

<p>obj1.mem1</p> Signup and view all the answers

Match the following struct names with their use case:

<p>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</p> Signup and view all the answers

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

<p>Member values can be accessed directly using their names. (C)</p> Signup and view all the answers

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

<p>True (A)</p> Signup and view all the answers

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

<p>To define how operators behave for the custom type.</p> Signup and view all the answers

Flashcards

Custom Data Types

A data type in C++ that enables programmers to create custom data structures tailored to specific programing needs.

Rational Numbers

A data type that represents fractions, where the numerator and denominator are integers. It can be a powerful tool for computations involving fractions.

Building Custom Types

The process of defining a new data type in C++ using existing data types and functionalities. It allows programs to handle specific data types not provided by the language.

Built-in Data Types

The inherent data types provided by a programming language. They offer common ways to represent data like integers, floating-point numbers, characters, or booleans.

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Example Usage

A C++ code snippet that demonstrates the intended usage and operation of a user-defined or built-in datatype. This helps visualize the real-world application of the datatype.

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Recursion

A programming technique where a function calls itself within its own definition, creating a cycle of execution.

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Divide and Conquer

A recursive approach that breaks a problem into smaller, similar subproblems until a base case is reached.

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Decrease and Conquer

A recursive approach that solves a problem by reducing the input size towards a base case.

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Iteration

A method of solving problems by repeatedly executing a sequence of instructions until a specific condition is met.

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Sum of Vector

A problem that involves calculating the sum of all elements in a given vector.

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Recursive Sum of Vector (Variant 1)

A recursive approach to calculate the sum of a vector by breaking it down into subproblems, each calculating the sum of a sub-vector.

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Recursive Sum of Vector (Variant 2)

A recursive approach to calculate the sum of a vector using a 'divide and conquer' strategy, splitting the vector into two halves and recursively calculating their sums.

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Base Case

The specific conditions that define when a recursive function stops calling itself and returns a value.

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Recursive Step

The part of a recursive function that handles the original problem by breaking it down into smaller subproblems.

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Divide and Conquer

A method of solving a problem by breaking it down into smaller and simpler subproblems.

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Recomputing Subproblems

The process of calculating the same value multiple times within a recursive function, leading to inefficiency.

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Fibonacci Numbers

A sequence where each number is the sum of the two preceding ones.

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Recursive Fibonacci Function

A recursive function that calculates the nth Fibonacci number by adding the two preceding numbers.

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Naive Fibonacci Algorithm

An inefficient way to calculate Fibonacci numbers, as it repeatedly calculates the same subproblems, leading to exponential time complexity.

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Iterative Fibonacci Algorithm

An efficient way to calculate Fibonacci numbers by iteratively calculating each value only once, resulting in linear time complexity.

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Recursion Tree

A technique for understanding recursive functions by visualizing the calls and their relationships.

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Recursion Depth

The maximum depth of recursive calls in a function.

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Parallelizability

The ability to divide a problem into multiple subproblems that can be solved concurrently, improving performance.

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struct

A user-defined data type in C++ that allows grouping different data types together under a single name.

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struct object

A variable that is declared using a struct definition and can store data of the specified struct type.

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struct member

A member of a struct is a variable that is defined within the struct's definition. These are the individual data items that the struct holds.

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struct initialization

The process of assigning initial values to the members of a struct when it is created. It can be done during declaration or using an initializer list.

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Accessing struct members

Accessing a member variable of a struct using the dot (.) operator.

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Operator overloading in structs

A technique where the default behavior of operators (like = or ==) for a struct is redefined to behave according to the specific requirements of the struct's data.

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Default initialization of structs

When a struct is declared, its members are automatically initialized. For fundamental types (like int or float), this means they are uninitialized and may hold garbage values until assigned a value.

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Uninitialized member access

A common problem encountered when reading the value of an uninitialized member of a struct. This can lead to unexpected results or program crashes.

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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.

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Related Documents

Introduction to Computer Science PDF Fall 2024
Lecture 9: Recursion and Fibonacci Numbers PDF
Programmier-Befehle - Woche 9 PDF

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.

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