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Added heapqueue.del (#5289)

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Yuriy Glukhov 2017-01-27 09:22:17 +02:00 • committed by Andreas Rumpf
commit c8dcf8993f
1 changed files with 35 additions and 11 deletions
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46
lib/pure/collections/heapqueue.nim
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@ -58,7 +58,7 @@ proc siftup[T](heap: var HeapQueue[T], p: int) =
# to its final resting place (by sifting its parents down). # to its final resting place (by sifting its parents down).
heap[pos] = newitem heap[pos] = newitem
siftdown(heap, startpos, pos) siftdown(heap, startpos, pos)
proc push*[T](heap: var HeapQueue[T], item: T) = proc push*[T](heap: var HeapQueue[T], item: T) =
## Push item onto heap, maintaining the heap invariant. ## Push item onto heap, maintaining the heap invariant.
(seq[T](heap)).add(item) (seq[T](heap)).add(item)
@ -74,6 +74,12 @@ proc pop*[T](heap: var HeapQueue[T]): T =
else: else:
result = lastelt result = lastelt
proc del*[T](heap: var HeapQueue[T], index: int) =
## Removes element at `index`, maintaining the heap invariant.
swap(seq[T](heap)[^1], seq[T](heap)[index])
seq[T](heap).setLen(heap.len - 1)
heap.siftup(index)
proc replace*[T](heap: var HeapQueue[T], item: T): T = proc replace*[T](heap: var HeapQueue[T], item: T): T =
## Pop and return the current smallest value, and add the new item. ## Pop and return the current smallest value, and add the new item.
## This is more efficient than pop() followed by push(), and can be ## This is more efficient than pop() followed by push(), and can be
@ -95,13 +101,31 @@ proc pushpop*[T](heap: var HeapQueue[T], item: T): T =
return item return item
when isMainModule: when isMainModule:
# Simple sanity test block: # Simple sanity test
var heap = newHeapQueue[int]() var heap = newHeapQueue[int]()
let data = [1, 3, 5, 7, 9, 2, 4, 6, 8, 0] let data = [1, 3, 5, 7, 9, 2, 4, 6, 8, 0]
for item in data: for item in data:
push(heap, item) push(heap, item)
doAssert(heap[0] == 0) doAssert(heap[0] == 0)
var sort = newSeq[int]() var sort = newSeq[int]()
while heap.len > 0: while heap.len > 0:
sort.add(pop(heap)) sort.add(pop(heap))
doAssert(sort == @[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]) doAssert(sort == @[0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
block: # Test del
var heap = newHeapQueue[int]()
let data = [1, 3, 5, 7, 9, 2, 4, 6, 8, 0]
for item in data: push(heap, item)
heap.del(0)
doAssert(heap[0] == 1)
heap.del(seq[int](heap).find(7))
heap.del(seq[int](heap).find(5))
heap.del(seq[int](heap).find(6))
heap.del(seq[int](heap).find(2))
var sort = newSeq[int]()
while heap.len > 0:
sort.add(pop(heap))
doAssert(sort == @[1, 3, 4, 8, 9])