giles
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LSD radix sort over base 10 digits. Per pass:
- 10 bucket-refs created via Array.init 10 (fun _ -> ref []) (each
closure call yields a distinct list cell)
- scan array, append each value to its digit's bucket
- flatten buckets back to the array in order
Input [170;45;75;90;802;24;2;66]
Output [2;24;45;66;75;90;170;802]
Sentinel: a.(0) + a.(7)*1000 = 2 + 802*1000 = 802002.
Tests array-of-refs with !buckets.(d) deref, list-mode bucket
sort within in-place array sort, unused for-loop var (`for _ =
1 to maxd`).
159 baseline programs total.
41 lines
833 B
OCaml
41 lines
833 B
OCaml
let max_digit n arr =
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let m = ref arr.(0) in
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for i = 1 to n - 1 do
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if arr.(i) > !m then m := arr.(i)
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done;
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let d = ref 0 in
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let x = ref !m in
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while !x > 0 do
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d := !d + 1;
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x := !x / 10
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done;
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!d
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let radix_sort arr =
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let n = Array.length arr in
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let maxd = max_digit n arr in
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let exp = ref 1 in
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for _ = 1 to maxd do
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let buckets = Array.init 10 (fun _ -> ref []) in
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for i = 0 to n - 1 do
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let digit = (arr.(i) / !exp) mod 10 in
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let b = buckets.(digit) in
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b := arr.(i) :: !b
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done;
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let k = ref 0 in
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for d = 0 to 9 do
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let xs = List.rev !(buckets.(d)) in
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List.iter (fun v ->
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arr.(!k) <- v;
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k := !k + 1
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) xs
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done;
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exp := !exp * 10
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done
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;;
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let a = [| 170; 45; 75; 90; 802; 24; 2; 66 |] in
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radix_sort a;
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a.(0) + a.(7) * 1000
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