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March 2014 update

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Ingy döt Net 2014-04-02 16:56:35 +00:00
parent 09687c4926
commit a25938f123
1846 changed files with 21876 additions and 5203 deletions
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48
Task/Prime-decomposition/Java/prime-decomposition-4.java
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@ -1,11 +1,43 @@
public static List<BigInteger> primeFactorBig(BigInteger a){
List<BigInteger> ans = new LinkedList<BigInteger>();
private static final BigInteger TWO = BigInteger.valueOf(2);
private static final BigInteger THREE = BigInteger.valueOf(3);
private static final BigInteger FIVE = BigInteger.valueOf(5);
for(BigInteger divisor = BigInteger.valueOf(2);
a.compareTo(ONE) > 0; divisor = divisor.add(ONE))
while(a.mod(divisor).equals(ZERO)){
ans.add(divisor);
a = a.divide(divisor);
public static ArrayList<BigInteger> primeDecomp(BigInteger n){
if(n.compareTo(TWO) < 0) return null;
ArrayList<BigInteger> factors = new ArrayList<BigInteger>();
// handle even values
while(n.and(BigInteger.ONE).equals(BigInteger.ZERO)){
n = n.shiftRight(1);
factors.add(TWO);
}
// handle values divisible by three
while(n.mod(THREE).equals(BigInteger.ZERO)){
factors.add(THREE);
n = n.divide(THREE);
}
// handle values divisible by five
while(n.mod(FIVE).equals(BigInteger.ZERO)){
factors.add(FIVE);
n = n.divide(FIVE);
}
// much like how we can skip multiples of two, we can also skip
// multiples of three and multiples of five. This increment array
// helps us to accomplish that
int[] pattern = {4,2,4,2,4,6,2,6};
int pattern_index = 0;
BigInteger current_test = BigInteger.valueOf(7);
while(!n.equals(BigInteger.ONE)){
while(n.mod(current_test).equals(BigInteger.ZERO)){
factors.add(current_test);
n = n.divide(current_test);
}
return ans;
current_test = current_test.add(BigInteger.valueOf(pattern[pattern_index]));
pattern_index = (pattern_index + 1) & 7;
}
return factors;
}