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replace a-e indices w/ 0-4

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This commit is contained in:
Martin Nowak 2016-09-25 11:10:42 +02:00
parent 56f511c020
commit 5901459850
1 changed files with 25 additions and 26 deletions
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51
std/algorithm/sorting.d
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@ -1358,54 +1358,53 @@ Sorts the first 5 elements exactly of range r.
private void sort5(alias lt, Range)(Range r) private void sort5(alias lt, Range)(Range r)
{ {
assert(r.length >= 5); assert(r.length >= 5);
enum a = 0, b = 1, c = 2, d = 3, e = 4;
version(unittest) scope(success) version(unittest) scope(success)
assert(!lt(r[b], r[a]) && !lt(r[c], r[b]) assert(!lt(r[1], r[0]) && !lt(r[2], r[1])
&& !lt(r[d], r[c]) && !lt(r[e], r[d])); && !lt(r[3], r[2]) && !lt(r[4], r[3]));
import std.algorithm : swapAt; import std.algorithm : swapAt;
// 1. Sort first two pairs // 1. Sort first two pairs
if (lt(r[b], r[a])) r.swapAt(a, b); if (lt(r[1], r[0])) r.swapAt(0, 1);
if (lt(r[d], r[c])) r.swapAt(c, d); if (lt(r[3], r[2])) r.swapAt(2, 3);
// 2. Arrange first two pairs by the largest element // 2. Arrange first two pairs by the largest element
if (lt(r[d], r[b])) if (lt(r[3], r[1]))
{ {
r.swapAt(a, c); r.swapAt(0, 2);
r.swapAt(b, d); r.swapAt(1, 3);
} }
assert(!lt(r[b], r[a]) && !lt(r[d], r[b]) && !lt(r[d], r[c])); assert(!lt(r[1], r[0]) && !lt(r[3], r[1]) && !lt(r[3], r[2]));
// 3. Insert e into [a, b, d] // 3. Insert 4 into [0, 1, 3]
if (lt(r[e], r[b])) if (lt(r[4], r[1]))
{ {
r.swapAt(d, e); r.swapAt(3, 4);
r.swapAt(b, d); r.swapAt(1, 3);
if (lt(r[b], r[a])) if (lt(r[1], r[0]))
{ {
r.swapAt(a, b); r.swapAt(0, 1);
} }
} }
else if (lt(r[e], r[d])) else if (lt(r[4], r[3]))
{ {
r.swapAt(d, e); r.swapAt(3, 4);
} }
assert(!lt(r[b], r[a]) && !lt(r[d], r[b]) && !lt(r[e], r[d])); assert(!lt(r[1], r[0]) && !lt(r[3], r[1]) && !lt(r[4], r[3]));
// 4. Insert c into [a, b, d, e] (note: we already know the last is greater) // 4. Insert 2 into [0, 1, 3, 4] (note: we already know the last is greater)
assert(!lt(r[e], r[c])); assert(!lt(r[4], r[2]));
if (lt(r[c], r[b])) if (lt(r[2], r[1]))
{ {
r.swapAt(b, c); r.swapAt(1, 2);
if (lt(r[b], r[a])) if (lt(r[1], r[0]))
{ {
r.swapAt(a, b); r.swapAt(0, 1);
} }
} }
else if (lt(r[d], r[c])) else if (lt(r[3], r[2]))
{ {
r.swapAt(c, d); r.swapAt(2, 3);
} }
// 7 comparisons, 0-9 swaps // 7 comparisons, 0-9 swaps
} }