Consider the following pseudocode function BAR given below. (Note: the "end" statement simply signals the end of the relevant "for" loop.) // BAR : N → N Function BAR(n): x 0 for k = {1, 2,...,n} do t←0 for i = {1, 2,..., k} do It+t+i end xx+t end return x (a) A precondition for BAR is that ne N. One postcondition for BAR is that x = N, but this postcondition isn't very insightful. Provide a postcondition that accurately describes the value x in terms of the input n. (b) Provide an exact value (in terms of n) for the total number of + operations performed by BAR. (c) Provide a Big-O estimate (in terms of n) for total the number of + operations performed by BAR.
Consider the following pseudocode function BAR given below. (Note: the "end" statement simply signals the end of the relevant "for" loop.) // BAR : N → N Function BAR(n): x 0 for k = {1, 2,...,n} do t←0 for i = {1, 2,..., k} do It+t+i end xx+t end return x (a) A precondition for BAR is that ne N. One postcondition for BAR is that x = N, but this postcondition isn't very insightful. Provide a postcondition that accurately describes the value x in terms of the input n. (b) Provide an exact value (in terms of n) for the total number of + operations performed by BAR. (c) Provide a Big-O estimate (in terms of n) for total the number of + operations performed by BAR.
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
Chapter1: Introduction
Section: Chapter Questions
Problem 1PE
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![### Pseudocode Function Analysis: BAR Function
Consider the following pseudocode function BAR given below. (Note: the "end" statement simply signals the end of the relevant "for" loop.)
```plaintext
// BAR : ℕ → ℕ
Function BAR(n):
x ← 0
for k ∈ {1, 2, ..., n} do
t ← 0
for i ∈ {1, 2, ..., k} do
t ← t + i
end
x ← x + t
end
return x
```
#### Analysis:
(a) A precondition for BAR is that \( n \in \mathbb{N} \). One postcondition for BAR is that \( x \in \mathbb{N} \), but this postcondition isn't very insightful. Provide a postcondition that accurately describes the value \( x \) in terms of the input \( n \).
**Postcondition Analysis:**
The outer loop runs from 1 to \( n \). For each \( k \), the inner loop calculates the sum of the first \( k \) natural numbers, which is given by the formula \( \frac{k(k+1)}{2} \). This sum is stored in \( t \) and then added to \( x \). Therefore, by the end of the function, \( x \) will be the sum of the series:
\[ x = \sum_{k=1}^{n} \frac{k(k+1)}{2} \]
(b) Provide an exact value (in terms of \( n \)) for the total number of \( + \) operations performed by BAR.
**Exact Value Calculation:**
The number of \( + \) operations can be split into two parts:
1. The \( + \) operations in the inner loop for calculating \( t \),
2. The \( + \) operation for updating \( x \).
For the inner loop:
- When \( k = 1 \), there is 1 \( + \) operation.
- When \( k = 2 \), there are 2 \( + \) operations.
- When \( k = 3 \), there are 3 \( + \) operations.
- ...
- When \( k = n \), there are \( n \) \( + \) operations.
Thus, the total for the inner loop is:
\[ \sum_{k](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fbbff2935-77bb-4550-bfd1-d595e6271f30%2F28889aad-3b8b-4140-9b46-d62003823b5a%2Ffmg9vqc_processed.png&w=3840&q=75)
Transcribed Image Text:### Pseudocode Function Analysis: BAR Function
Consider the following pseudocode function BAR given below. (Note: the "end" statement simply signals the end of the relevant "for" loop.)
```plaintext
// BAR : ℕ → ℕ
Function BAR(n):
x ← 0
for k ∈ {1, 2, ..., n} do
t ← 0
for i ∈ {1, 2, ..., k} do
t ← t + i
end
x ← x + t
end
return x
```
#### Analysis:
(a) A precondition for BAR is that \( n \in \mathbb{N} \). One postcondition for BAR is that \( x \in \mathbb{N} \), but this postcondition isn't very insightful. Provide a postcondition that accurately describes the value \( x \) in terms of the input \( n \).
**Postcondition Analysis:**
The outer loop runs from 1 to \( n \). For each \( k \), the inner loop calculates the sum of the first \( k \) natural numbers, which is given by the formula \( \frac{k(k+1)}{2} \). This sum is stored in \( t \) and then added to \( x \). Therefore, by the end of the function, \( x \) will be the sum of the series:
\[ x = \sum_{k=1}^{n} \frac{k(k+1)}{2} \]
(b) Provide an exact value (in terms of \( n \)) for the total number of \( + \) operations performed by BAR.
**Exact Value Calculation:**
The number of \( + \) operations can be split into two parts:
1. The \( + \) operations in the inner loop for calculating \( t \),
2. The \( + \) operation for updating \( x \).
For the inner loop:
- When \( k = 1 \), there is 1 \( + \) operation.
- When \( k = 2 \), there are 2 \( + \) operations.
- When \( k = 3 \), there are 3 \( + \) operations.
- ...
- When \( k = n \), there are \( n \) \( + \) operations.
Thus, the total for the inner loop is:
\[ \sum_{k
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