giles
b240408a4c
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Binary search in a rotated sorted array. Standard sorted-half
test at each step:
if arr.(lo) <= arr.(mid) then
left half [lo, mid] is sorted -> check whether target is in it
else
right half [mid, hi] is sorted -> check whether target is in it
For [4; 5; 6; 7; 0; 1; 2]:
search 0 -> index 4
search 7 -> index 3
search 3 -> -1 (absent)
Encoded fingerprint: 4 + 3*10 + (-1)*100 = -66.
First baseline returning a negative top-level value; the runner
uses literal grep -qF so leading minus parses fine.
196 baseline programs total.
26 lines
647 B
OCaml
26 lines
647 B
OCaml
let bs_rotated arr target =
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let lo = ref 0 in
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let hi = ref (Array.length arr - 1) in
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let result = ref (-1) in
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while !lo <= !hi && !result = -1 do
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let mid = (!lo + !hi) / 2 in
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if arr.(mid) = target then result := mid
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else if arr.(!lo) <= arr.(mid) then begin
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if target >= arr.(!lo) && target < arr.(mid) then
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hi := mid - 1
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else
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lo := mid + 1
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end else begin
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if target > arr.(mid) && target <= arr.(!hi) then
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lo := mid + 1
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else
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hi := mid - 1
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end
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done;
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!result
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;;
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let a = [| 4; 5; 6; 7; 0; 1; 2 |] in
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bs_rotated a 0 + bs_rotated a 7 * 10 + bs_rotated a 3 * 100
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