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TASK #1 - Calculator
You are given a string, $s, containing mathematical expression.
Write a script to print the result of the mathematical expression. To
keep it simple, please only accept + - * ().
Example 1:
Input: $s = "10 + 20 - 5"
Output: 25
Example 2:
Input: $s = "(10 + 20 - 5) * 2"
Output: 50
MY NOTES: Ok, so a mini parser of a string in one or more command
line arguments. What's the easiest way?
- use Parse::RecDescent?
- hand write a recursive descent parser?
- convert to RPN and evaluate RPN?
TASK #2 - Stealthy Number
You are given a positive number, $n.
Write a script to find out if the given number is Stealthy Number.
A positive integer N is stealthy, if there exist positive integers
a, b, c, d such that a * b = c * d = N and a + b = c + d + 1.
Example 1
Input: $n = 36
Output: 1
Since 36 = 4 (a) * 9 (b) = 6 (c) * 6 (d) and
4 (a) + 9 (b) = 6 (c) + 6 (d) + 1.
Example 2
Input: $n = 12
Output: 1
Since 2 * 6 = 3 * 4 and 2 + 6 = 3 + 4 + 1
Example 3
Input: $n = 6
Output: 0
Since 2 * 3 = 1 * 6 but 2 + 3 != 1 + 6 + 1
MY NOTES: hmm.. need some kind of brute force search, presumably.
what are the limits of a..d? first thought: each <= $n,
hang on, (a,b) must be a factor pair of n (where a is a factor of n
<= sqrt(n) and b is n/a), and (c,d) must also be a factor pair of n.
As a bonus, I've also implemented the --firstn flag which makes it
find and display the first $n stealthy numbers.
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