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Scaled-down Project Euler #4. Real version uses 3-digit numbers yielding 906609 = 913 * 993; that's an 810k-iteration nested loop that times out under our contended-host spec-level evaluator. The 2-digit version (10..99) is fast enough and tests the same algorithm: 9009 = 91 * 99 (the only 2-digit-product palindrome > 9000) Implementation: is_pal n index-walk comparing s.[i] to s.[len-1-i] euler4 lo hi nested for with running max + early-skip via 'p > !m && is_pal p' short-circuit 111 baseline programs total.
22 lines
374 B
OCaml
22 lines
374 B
OCaml
let is_pal n =
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let s = string_of_int n in
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let len = String.length s in
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let p = ref true in
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for i = 0 to len / 2 - 1 do
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if s.[i] <> s.[len - 1 - i] then p := false
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done;
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!p
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let euler4 lo hi =
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let m = ref 0 in
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for a = lo to hi do
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for b = a to hi do
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let p = a * b in
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if p > !m && is_pal p then m := p
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done
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done;
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!m
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;;
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euler4 10 99
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