A permutation is an ordered arrangement of objects. For example, 3124 is one possible permutation of the digits 1, 2, 3 and 4. If all of the permutations are listed numerically or alphabetically, we call it lexicographic order. The lexicographic permutations of 0, 1 and 2 are:
012 021 102 120 201 210
What is the millionth lexicographic permutation of the digits 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9?
Permalink: http://projecteuler.net/problem=24
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Recently, I've re-read awesome java book Effective Java by Joshua Bloch. The book contains 78 independent items, discussing various aspects of programming in java. Something like mini-design patterns with emphasis on their pros and cons.
Few notes from each item as a refresher.
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Programming Sucks.
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Clojure is a great language, and as every language, it has some unobvious and strange things, which seem confusing.
Some of such things are gathered here. Most of them encountered by stupidity, docs misunderstanding, clojure specifics and procrastination.
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Find the sum of all the positive integers which cannot be written as the sum of two abundant numbers.
Permalink: http://projecteuler.net/problem=23
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Numberto has new features!
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How to live in the Kingdom of Nouns, why mathematicians cry, filling gaps in algorithms, portion of clojure, STM, HTTP and more.
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Using names.txt a 46K text file containing over five-thousand first names, begin by sorting it into alphabetical order. Then working out the alphabetical value for each name, multiply this value by its alphabetical position in the list to obtain a name score.
For example, when the list is sorted into alphabetical order, COLIN, which is worth 3 + 15 + 12 + 9 + 14 = 53, is the 938th name in the list. So, COLIN would obtain a score of 938 x 53 = 49714.
What is the total of all the name scores in the file?
Permalink: http://projecteuler.net/problem=22
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Evaluate the sum of all the amicable numbers under 10000.
Permalink: http://projecteuler.net/problem=21
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All you need to play with numbers!
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