a. What is the recurrence relation? b. Solve the recurrence relation from (a) in terms of n and show the O(

Database System Concepts
7th Edition
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
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### Algorithm Analysis Exercise

**Problem Statement:**

1. Consider the following program:

```plaintext
Algorithm recursive (int n){
    IF n <= 3 then
        return (0);
    ELSE
        recursive(n/3);
        recursive(n/3);
        recursive(n/3);
        FOR i = 1 to n
            do something;
        ENDFOR
    ENDIF
}
```

**Questions:**

a. What is the recurrence relation?

b. Solve the recurrence relation from (a) in terms of *n* and show the O( ) notation.

**Explanation:**

The provided algorithm is a recursive function that executes different operations based on the value of *n*. If *n* is less than or equal to 3, the function terminates by returning 0. If *n* is greater than 3, the function calls itself three times with a reduced argument, `n/3`, and performs a loop that runs *n* times to "do something."

**Recurrence Relation Analysis:**

- **Base Case:** When *n* is less than or equal to 3, the operation completes in constant time *O(1)*.
- **Recursive Case:**
  - Calls the recursive function thrice for inputs reduced to *n/3*.
  - Executes an additional loop that operates in *O(n)* time.

The recurrence relation, therefore, can be expressed as:
\[ T(n) = 3T(n/3) + O(n) \]

**Solution Approach:**

To solve this recurrence relation, you might employ the Master Theorem, which provides a way to solve recurrences of the form:
\[ T(n) = aT(n/b) + f(n) \]

In this example, we identify:
- \( a = 3 \): Number of recursive calls
- \( b = 3 \): Factor by which the subproblem size is reduced
- \( f(n) = O(n) \): Additional cost outside the recursive calls

Using the Master Theorem's criteria:
- Compare \( f(n) \) = \( O(n) \) with \( n^{\log_b a} = n^{\log_3 3} = n^1 \)

Here, \( f(n) = \Theta(n^1) \), fitting the criteria for \( f(n) = \Theta(n^{\log_b a}) \). According to
Transcribed Image Text:### Algorithm Analysis Exercise **Problem Statement:** 1. Consider the following program: ```plaintext Algorithm recursive (int n){ IF n <= 3 then return (0); ELSE recursive(n/3); recursive(n/3); recursive(n/3); FOR i = 1 to n do something; ENDFOR ENDIF } ``` **Questions:** a. What is the recurrence relation? b. Solve the recurrence relation from (a) in terms of *n* and show the O( ) notation. **Explanation:** The provided algorithm is a recursive function that executes different operations based on the value of *n*. If *n* is less than or equal to 3, the function terminates by returning 0. If *n* is greater than 3, the function calls itself three times with a reduced argument, `n/3`, and performs a loop that runs *n* times to "do something." **Recurrence Relation Analysis:** - **Base Case:** When *n* is less than or equal to 3, the operation completes in constant time *O(1)*. - **Recursive Case:** - Calls the recursive function thrice for inputs reduced to *n/3*. - Executes an additional loop that operates in *O(n)* time. The recurrence relation, therefore, can be expressed as: \[ T(n) = 3T(n/3) + O(n) \] **Solution Approach:** To solve this recurrence relation, you might employ the Master Theorem, which provides a way to solve recurrences of the form: \[ T(n) = aT(n/b) + f(n) \] In this example, we identify: - \( a = 3 \): Number of recursive calls - \( b = 3 \): Factor by which the subproblem size is reduced - \( f(n) = O(n) \): Additional cost outside the recursive calls Using the Master Theorem's criteria: - Compare \( f(n) \) = \( O(n) \) with \( n^{\log_b a} = n^{\log_3 3} = n^1 \) Here, \( f(n) = \Theta(n^1) \), fitting the criteria for \( f(n) = \Theta(n^{\log_b a}) \). According to
Expert Solution
Step 1

1. Recurrence Relation can be defined as

"an equation that recursively defines a progression or multi-dimensional array of values, in which one or more primary terms are specified; each additional term of the sequence or array is distinct as a function of the previous terms."

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