Contents tagged with Project Euler
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A cool way to find out whether a number is palindromic
In this blog entry I proposed a solution to Problem 4 at Project Euler, a crucial element of the problem is to find out whether a number is a palindrome (909 is, 809 isn't), a bit out of laziness and a bit in order to reuse existing methods, I decided to verify the palindrome by converting the number into a char array and then comparing this array with its mirror version, it works but it's not really that mathematical... Dustin Campbell proposed a solution kind of similar to mine (alas, more elegant and, above that, in F#) and using the same trick of converting the number to chars, as he didn't like this part of the solution, in this new blog entry he proposes the detection of a palindrome by mirroring the number one digit at a time. A translation of his F# code to C# 3.0 could be:
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New version of F# just released
In its way from research language to commercial language, Don Syme just announced that, silently, on May the 1st version 1.9.4.15 of F# was released.
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Which is the ten thousand first prime?
Prime numbers have a good deal of practical applications (for example in cryptography) but let's face it, even if they would have none, they would still be the favorite toy of mathematicians. In Problem 7 of Project Euler, we are asked to find the 10001st element of the famous list, my approach was this:
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The square of the sum vs. the sum of the squares
The sixth Project Euler problem poses an exercise that, to me, offers no major hurdles:
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Recursive lambdas and sequence aggregations
The fifth problem at Project Euler proposes this nostalgic primary school exercise: find the smallest quantity that is evenly divisible by some numbers, the least common multiple of 1, 2, 3, ..., 20 to be precise. To begin with, let's remember the old arithmetic formula:
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Nested sequences and palindrome numbers
Problem 4 of Project Euler poses and impractical albeit intriguing problem: given all three digit numbers (100, 101, 102, ..., 998, 999), find the largest product of 2 of those numbers, where the product is a palindrome. For example, 580.085 is the product of two three-digit numbers (995 x 583) but it isn't the largest of such products. One possible functional C# solution is: