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17 lines
417 B
17 lines
417 B
11 months ago
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use std::collections::HashSet;
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fn main() {
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let mut ps = HashSet::new();
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let mut hs = HashSet::new();
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let N = 500000u64;
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for n in 1..N { hs.insert(n*(2*n-1)); }
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for n in 1..N { ps.insert(n*(3*n -1)/2 ); }
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for n in 286u64..N {
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let tn = n * (n+1)/2;
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if !hs.contains(&tn) { continue; }
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if !ps.contains(&tn) { continue; }
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println!("{}", tn);
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break;
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}
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}
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