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This commit is contained in:
Andrei Alexandrescu 2009-05-01 00:59:41 +00:00
parent ee67c6cb0e
commit edd4c82776
1 changed files with 39 additions and 13 deletions
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52
std/algorithm.d
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@ -5185,13 +5185,19 @@ result directly in $(D tgt) and requires no extra memory).
Warning: Because $(D largestPartialIntersection) does not allocate Warning: Because $(D largestPartialIntersection) does not allocate
extra memory, it will leave $(D ror) modified. Namely, by the time $(D extra memory, it will leave $(D ror) modified. Namely, by the time $(D
largestPartialIntersection) returns, all ranges in $(D ror) will have largestPartialIntersection) returns, all ranges in $(D ror) will have
been advanced until they are empty. To avoid that, duplicate $(D ror) been advanced until they are empty. If you want $(D ror) to preserve
prior to calling (and perhaps cache the duplicate in between calls). its contents after the call, pass a duplicate to $(D
largestPartialIntersection) (and perhaps cache the duplicate in
between calls).
*/ */
void largestPartialIntersection void largestPartialIntersection
(alias less = "a < b", RangeOfRanges, Range) (alias less = "a < b", RangeOfRanges, Range)
(RangeOfRanges ror, Range tgt, bool sorted = false) (RangeOfRanges ror, Range tgt, bool sorted = false)
{ {
// Preemptively get rid of all empty ranges in the input
// No need for stability either
ror = remove!("a.empty", SwapStrategy.unstable)(ror);
alias binaryFun!less comp; alias binaryFun!less comp;
alias ElementType!(ElementType!RangeOfRanges) E; alias ElementType!(ElementType!RangeOfRanges) E;
alias ElementType!Range InfoType; alias ElementType!Range InfoType;
@ -5200,24 +5206,44 @@ void largestPartialIntersection
return a.field[1] > b.field[1]; return a.field[1] > b.field[1];
} }
auto heap = BinaryHeap!(Range, heapComp)(tgt, 0); auto heap = BinaryHeap!(Range, heapComp)(tgt, 0);
bigloop:
for (;;) for (;;)
{ {
auto tr = frontTransversal(ror); auto tr = frontTransversal!(TransverseOptions.assumeNotJagged)(ror);
if (tr.empty) break; if (tr.empty) break;
auto mc = minCount!less(tr); auto mc = minCount!less(tr);
//auto cm = tuple(mc.field[1], mc.field[0]);
// auto cnt = mc.field[1];
// writeln(min);
// writeln(cnt);
// Put that on the heap
heap.conditionalPut(mc); heap.conditionalPut(mc);
// Now remove that minimum element from wherever it occurred // Now remove that minimum element from wherever it occurred
foreach (ref r; ror) for (size_t i = 0; i < ror.length; )
{ {
if (r.empty) continue; auto r = &ror[i];
if (!comp(r.front, mc.field[0]) if ((*r).empty)
&& !comp(mc.field[0], r.front)) {
r.popFront; // this ought to be removed
swap(*r, ror.back);
ror.popBack;
if (i == ror.length)
{
// get outta here for good
break bigloop;
}
// no increment for i, revisit this guy and see what happens
continue;
}
if (!comp(mc.field[0], (*r).front))
{
// this guy is equal to the minimum
(*r).popFront;
// if ror[i] is empty, revisit because we want to get
// rid of it
if (! (*r).empty) ++i;
}
else
{
// normal case: nonempty range and no removal, just
// move on
++i;
}
} }
} }
if (sorted) heap.pop(heap.length); if (sorted) heap.pop(heap.length);