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let palindrome_sum lo hi =
let total = ref 0 in
for n = lo to hi do
if is_pal n then total := !total + n
done;
!total
palindrome_sum 100 999 = 49500
There are 90 three-digit palindromes (form aba; 9 choices for a, 10
for b). Average value 550, sum 49500.
Companion to palindrome.ml (predicate-only) and paren_depth.ml.
127 baseline programs total.
20 lines
347 B
OCaml
20 lines
347 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 palindrome_sum lo hi =
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let total = ref 0 in
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for n = lo to hi do
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if is_pal n then total := !total + n
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done;
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!total
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;;
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palindrome_sum 100 999
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