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401
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1 |
// Core Part 1 about the 3n+1 conjecture
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433
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2 |
//============================================
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3 |
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4 |
object C1 {
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5 |
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472
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6 |
def collatz(n: Long): Long =
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7 |
if (n == 1) 0 else
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8 |
if (n % 2 == 0) 1 + collatz(n / 2) else
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9 |
1 + collatz(3 * n + 1)
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208
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10 |
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11 |
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472
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12 |
def collatz_max(bnd: Long): (Long, Long) = {
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val all = for (i <- (1L to bnd)) yield (collatz(i), i)
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14 |
all.maxBy(_._1)
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463
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15 |
}
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363
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16 |
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472
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17 |
def is_pow(n: Long) : Boolean = (n & (n - 1)) == 0
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18 |
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19 |
def is_hard(n: Long) : Boolean = is_pow(3 * n + 1)
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363
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20 |
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472
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21 |
def last_odd(n: Long) : Long =
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if (is_hard(n)) n else
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if (n % 2 == 0) last_odd(n / 2) else
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24 |
last_odd(3 * n + 1)
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335
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25 |
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363
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26 |
}
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335
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27 |
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28 |
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29 |
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433
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30 |
// This template code is subject to copyright
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31 |
// by King's College London, 2022. Do not
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32 |
// make the template code public in any shape
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// or form, and do not exchange it with other
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34 |
// students under any circumstance.
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