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38 lines
991 B
38 lines
991 B
type CZS = Vec<Option<u32>>; |
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struct Collatz { czs: CZS } |
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impl Collatz { |
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pub fn new() -> Collatz { |
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let cl0 = Some(0); // for indexing |
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let cl1 = Some(1); |
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Collatz { czs: vec![cl0, cl1] } |
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} |
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pub fn compute(&mut self, n: usize) -> u32 { |
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match self.ensure_get(n) { |
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Some(cl) => cl, |
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None => { |
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//println!("compute {}", n); |
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let cl_prev = if n % 2 == 0 { |
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self.compute(n / 2) |
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} else { |
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self.compute(3 * n + 1) |
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}; |
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self.czs[n] = Some(cl_prev + 1); |
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cl_prev + 1 |
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} |
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} |
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} |
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pub fn ensure_get(&mut self, i: usize) -> Option<u32> { |
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while self.czs.len() <= i { self.czs.push(None); } |
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self.czs[i] |
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} |
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} |
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fn main() { |
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let mut collatz = Collatz::new(); |
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for k in 0..100000usize { |
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let clk = collatz.compute(k); |
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println!("{}: {}", k, clk); |
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} |
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}
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