Recursion in Programming

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Questions and Answers

What is a defining characteristic of a recursive function?

  • It performs iterative processes only.
  • It relies on external functions for completion.
  • It calls itself until it reaches a base case. (correct)
  • It calls itself indefinitely without a base case.

Which part of recursion defines the stopping condition?

  • Function case
  • Base case (correct)
  • Return case
  • Recursive case

In what type of recursion does a function call itself directly?

  • Head recursion
  • Tail recursion
  • Indirect recursion
  • Direct recursion (correct)

What is the factorial of 0 according to the recursive definition?

<p>1 (B)</p> Signup and view all the answers

What is the first step in writing a recursion algorithm?

<p>Define the base case (D)</p> Signup and view all the answers

For the factorial function, how is the recursive case expressed?

<p>n! = n x (n - 1)! (B)</p> Signup and view all the answers

What must be handled correctly in a recursive function to ensure correct execution?

<p>Return values from each call. (D)</p> Signup and view all the answers

Which type of recursion is characterized by the last operation of a function being a call to itself?

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

What is the main characteristic of tail recursion?

<p>The recursive call must be the last operation performed before returning. (A)</p> Signup and view all the answers

In the provided example of head recursion, what operation occurs during the recursive call?

<p>No operation is performed until the return phase. (B)</p> Signup and view all the answers

Which type of recursion involves multiple calls to the function within each recursive execution?

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

How does indirect recursion differ from direct recursion?

<p>Indirect recursion calls another function that calls the original function. (A)</p> Signup and view all the answers

In the tail recursion example, what parameters does the helper function receive?

<p>The current number and an accumulator. (D)</p> Signup and view all the answers

Which of the following statements is true about head recursion?

<p>It recurses without performing any operations. (C)</p> Signup and view all the answers

What happens if the base case in a recursive function is not correctly defined?

<p>The function will lead to infinite recursion and eventually crash. (D)</p> Signup and view all the answers

What is the outcome of the nested factorial function when called with n = 3?

<p>6 (A)</p> Signup and view all the answers

What is the primary purpose of backtracking in algorithms?

<p>To try multiple options and find the best solution. (B)</p> Signup and view all the answers

In which situation would backtracking be particularly useful?

<p>Finding a path in a maze. (A)</p> Signup and view all the answers

Which of the following is NOT a step in the backtracking algorithm?

<p>Use dynamic programming. (C)</p> Signup and view all the answers

What is the initial state in the example provided for backtracking?

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

Which of the following correctly describes the purpose of the 'multiply' function in the example code?

<p>To calculate the product of two integers. (B)</p> Signup and view all the answers

What does the base case of the factorial function check for?

<p>If n is zero. (D)</p> Signup and view all the answers

Which of these fields uses recursion as described in the content?

<p>Graphics and mathematical calculations. (A)</p> Signup and view all the answers

What is the time complexity of the linear search example for backtracking given in the content?

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

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Study Notes

Recursion

  • A programming technique where a function calls itself to solve smaller instances of the same problem
  • Recursive function calls itself directly or indirectly
  • Base case: a condition that cannot be expressed in terms of a smaller version, stopping the recursion
  • Recursive case: the function calls itself with modified arguments, moving towards the base case

Types of Recursion

  • Direct recursion: a function calls itself directly
    • Tail recursion: function calls happen at the last statement, no further operations after recursion
    • Head recursion: function calls happen at the first statement, no operations before recursion
    • Tree recursion: a function makes one or more calls to itself within the function
    • Nested recursion: the function makes a call to another function that in turn calls the original function
  • Indirect recursion: a function calls another function that eventually calls the original function, forming a cycle

Example of Recursive Factorial Function

  • Factorial of a non-negative integer n: n! = n x (n - 1)!
  • Base case: 0! = 1
  • Recursive case: n! = n x (n - 1)! for n > 0

Applications of Recursion

  • Search and sorting algorithms
  • Mathematical calculations
  • Compiler design
  • Graphics
  • Artificial intelligence

Backtracking

  • A problem-solving strategy exploring different options to find the best solution
  • Systematically tries all available avenues from a point, backtracking when dead ends are reached
  • Aims to find a solution or exhaust all possibilities
  • Introduced by Dr. D.H. Lehmer in 1950s
  • Algorithm description developed by R.J. Walker in 1960s
  • Further developed by S. Golamb and L. Baumert

Steps for Implementing Backtracking Algorithm

  • Define the problem
  • Choose a representation
  • Define the state space
  • Define the initial state
  • Define the goal state
  • Implement the search
  • Check for termination conditions
  • Optimize the algorithm

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Related Documents

Recursion-and-Backtracking.pdf

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