Cycle detection: Difference between revisions

=={{header|Groovy}}==

{{trans|Java}}

<lang groovy>import java.util.function.IntUnaryOperator

class CycleDetection {

static void main(String[] args) {

brent({ i -> (i * i + 1) % 255 }, 3)

}

static void brent(IntUnaryOperator f, int x0) {

int cycleLength = -1

int hare = x0

FOUND:

for (int power = 1; ; power *= 2) {

int tortoise = hare

for (int i = 1; i <= power; i++) {

hare = f.applyAsInt(hare)

if (tortoise == hare) {

cycleLength = i

break FOUND

}

}

}

hare = x0

for (int i = 0; i < cycleLength; i++) {

hare = f.applyAsInt(hare)

}

int cycleStart = 0

for (int tortoise = x0; tortoise != hare; cycleStart++) {

tortoise = f.applyAsInt(tortoise)

hare = f.applyAsInt(hare)

}

printResult(x0, f, cycleLength, cycleStart)

}

static void printResult(int x0, IntUnaryOperator f, int len, int start) {

printf("Cycle length: %d%nCycle: ", len)

int n = x0

for (int i = 0; i < start + len; i++) {

n = f.applyAsInt(n)

if (i >= start) {

printf("%s ", n)

}

}

println()

}

}</lang>

{{out}}

<pre>Cycle length: 6

Cycle: 2 5 26 167 95 101 </pre>