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April 1, 2014 12:29
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Fibonacci Module, resolving Fib in Java.
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import java.lang.reflect.InvocationTargetException; | |
import java.util.WeakHashMap; | |
import java.util.concurrent.TimeUnit; | |
// @see http://java67.blogspot.sg/2012/07/java-program-fibonacci-series-with.html | |
// @see https://github.com/raganwald/homoiconic/blob/master/2008-12-12/fibonacci.md | |
public class FibonacciModule { | |
// Standard | |
public static Integer fibonacci(final Integer n) { | |
if (n < 2) { | |
return n; | |
} | |
return fibonacci(n - 1) + fibonacci(n - 2); | |
} | |
// Iterative | |
public static Integer ifibonacci(final Integer n) { | |
if (n < 2) { | |
return n; | |
} | |
Integer fib = 2, | |
fib1 = fib - 1, | |
fib2 = fib - 2; | |
for(int i = n; i > 0; i--) { | |
fib = fib1 + fib2; | |
fib1 = fib2; | |
fib2 = fib; | |
} | |
return fib; | |
} | |
// Memoized | |
public static WeakHashMap<Integer, Integer> m = new WeakHashMap<>(); | |
public static Integer mfibonacci(final Integer n) { | |
if (n < 2) { | |
return n; | |
} | |
if (m.containsKey(n)) { | |
return m.get(n); | |
} | |
m.put(n, mfibonacci(n -1) + mfibonacci(n - 2)); | |
return m.get(n); | |
} | |
// Power | |
public static Integer fibonnaci_power(Integer n) { | |
if (n < 2) { | |
return n; | |
} | |
Integer[] m = new Integer[]{1, 1, 0}; | |
return power(m, n-1)[0]; | |
} | |
// Naive Power | |
public static Integer fibonnaci_naive_power(Integer[] m, final Integer n) | |
{ | |
Object[] args = new Object[n - 1]; | |
for (Integer i = 0; i < n - 1; i++) { | |
args[i] = m; | |
} | |
Integer[] result = new Integer[]{0, 0, 0}; | |
try { | |
result = (Integer[]) | |
Fibonnaci.class | |
.getDeclaredMethod("times", Object[].class) | |
.invoke(Fibonnaci.class, new Object[] {args}); | |
} | |
catch (NoSuchMethodException ex) { | |
} | |
catch (IllegalAccessException e) { | |
} | |
catch (InvocationTargetException e) { | |
} | |
return result[0]; | |
} | |
public final static Integer[] power (Integer[] m, Integer n) { | |
if (n == 1) { | |
return m.clone(); | |
} | |
Integer[] halves = power(m, n / 2); | |
if ((n % 2) == 0) { | |
return times(halves, halves); | |
} | |
else { | |
return times(halves, halves, m); | |
} | |
} | |
public final static Integer[] times(Object ...ems) { | |
Integer[] p = null, // product | |
m = null; // matrix | |
Integer a, b, c, | |
d, e, f; | |
p = ((Integer[]) ems[0]).clone(); // shallow copy | |
for (int i = 1, l = ems.length; i < l; i++) { | |
m = ((Integer[]) ems[i]).clone(); | |
a = p[0]; b = p[1]; c = p[2]; | |
d = m[0]; e = m[1]; f = m[2]; | |
// a, b, c = p[0], p[1], p[2]; | |
// d, e, f = m[0], m[1], m[2]; | |
// [a*d + b*e, a*e + b*f, b*e + c*f] | |
p[0] = a * d + b * e; | |
p[1] = a * e + b * f; | |
p[2] = b * e + c * f; | |
} | |
return p; | |
} | |
public static void main(String[] args) { | |
Integer[] m = new Integer[]{1, 1, 0}; | |
Integer n = 43; | |
long nanoTime = System.nanoTime(); | |
System.out.println("Calculated fib(" + n + ") => " + fibonacci(n) + " in total: " + TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - nanoTime) + "ms"); | |
nanoTime = System.nanoTime(); | |
System.out.println("Calculated ifib(" + n + ") => " + ifibonacci(n) + " in total: " + TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - nanoTime) + "ms"); | |
nanoTime = System.nanoTime(); | |
System.out.println("Calculated mfib(" + n + ") => " + mfibonacci(n) + " in total: " + TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - nanoTime) + "ms"); | |
nanoTime = System.nanoTime(); | |
System.out.println("Calculated fib_power(" + n + ") => " + fibonnaci_power(n) + " in total: " + TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - nanoTime) + "ms"); | |
nanoTime = System.nanoTime(); | |
System.out.println("Calculated fib_naive_power(" + n + ") => " + fibonnaci_naive_power(m, n) + " in total: " + TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - nanoTime) + "ms"); | |
} | |
} |
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