Generate All Keys Using Armstrong Axion Algorithm
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- Generate All Keys Using Armstrong Axiom Algorithm For Sale
- Generate All Keys Using Armstrong Axion Algorithm Code
What is that all about?
The task is to generate Armstrong Numbers from 1 up to the length of N decimal digits.
Armstrong number (aka Narcissistic number) of length N digits is a number which is equal to the sum of its digits each in power of N. For example: 153 = 1^3 + 5^3 + 3^3 = 3 + 125 + 27 = 153
More info at wiki
Brute force algorithm
There is an obvious bruteforce algorithms that:
- Pre-generation of all powers i^j, where i is a digits, and j is possible length from 1 to N - this is necessary for all solutions
- For each integer i from 1 to K
- Divides i by digits
- Calculate power of each digit
- Sum up those powers
- If this sum is equal to i - add it to the result list
Implementation: ArmstrongNumbersBruteforce.java
Generate All Keys Using Armstrong Axiom Algorithm For Sale
It can be improved by parallel calculation of sum of digit powers to the number generation.
Implementation: ArmstrongNumbersBruteforceOpt.java
Hash Approach - Divide At Impera
There is another interesting idea of bruteforce approach improvement.
- Divide a number for two equal parts. In case of an odd N first part will be a bit longer. For example, if N=7, the number will be divide like XXXXYYY, where XXXX the first part (4 decimal digits), and YYY the second part with 3 digits.
- Generate all integers i of the second part (in our example there will be integers from 001 to 999).
- Calculate p equal to sum of digits in power of N.
- Add to some hash the following pair {p-i, i}. For example, for i=725, p=7^7+2^7+5^7=901796. We add pair {901071, 725}.
- Generate all integers i of the first part without leading zeros (in our example there will be integers from 1000 to 9999).
- Calculate p equal to sum of digits in power of N.
- Check if hash has a key of (i*10^(N/2)-p). For example, i=1741, thus p=1^7 + 7^7 + 4^7 + 1^7=839929. We look for key (1741000 - 839929) = (901071). OMG! It exists!!!
- In case that key exists we unite the Armstrong number from two parts and add it to the result list. 1741000 + 725 = 1741725
One addition, is that we cannot store simply (key, value), we need to store multiple values, for example to be able to generate 370 and 371.
Implementation: ArmstrongNumbersHash.java
Multi Sets Approach
We may note that for each multi-set of digits, like [1, 1, 2, 4, 5, 7, 7] there is only one sum of powers, which in its turn may either be or be not represented by the digits from set. In the example 1^7 + 1^7 + 2^7 + 4^7 + 5^7 + 7^7 + 7^7 = 1741725, which can be represented by the digits and thus is an Armstrong number.
We may build an algorighm basing on this consideration.
- For each number length from 1 to N
- Generate all possible multi-sets of N digits
- For each multi-set calculate sum of digits^N
- Check if it's possible to represent the number we got on step 4 with the digits from the multi-set
- If so - add the number to the result list
Complexity assestment The number of cases calculated for each length N is equal to the number of combinations (N + 9, 9) = (N+9)!/(9!N!). Thus for all Ns less than 10 we will generate 92,377 cases. For N<20: 20,030,009 cases.
Implementation: ArmstrongNumbersMultiSetLong.java
Generate All Keys Using Armstrong Axion Algorithm Code
Microsoft office 2013 activation key generator windows 8. With optimizations:
- For long: ArmstrongNumbersMultiSetLongOpt.java
- For BigInteger: ArmstrongNumbersMultiSetBigIntegerOpt.java
Benchmarking
Let's compare the algorithms performance for different numbers of length N. I did the tests with my MacBook Pro.
Algorithm | int (N<10) | long (N<20) | BigInteger (N<40) |
---|---|---|---|
Brute Force | ~55 seconds | few thousand years | N/A |
Improved Brute Force | ~3.7 s | ~300 years | N/A |
Hash Approach | 50 ms | OutOfMemoryException | N/A |
Multi-set Approach | 15 ms | ~1.1 s | N/A |
Multi-set Improved | 11 ms | ~550 ms | N/A |
Multi-set Improved BigInteger | ~100 ms | ~5.5 s | ~ 0.5 hours |
Clear win of the multi-set algorithm!