heapqueue

nimony/lib/std/heapqueue.nim

A min-heap (priority queue) implemented as a binary heap over a seq.

The smallest element (per <) is always at index 0, so pop returns elements in ascending order. The element type must be Comparable.

```
type HeapQueue = object
  data: seq[T]
```
func initHeapQueue(): HeapQueue[T]
Creates a new empty heap.
func len(heap: HeapQueue[T]): int64
Number of elements in heap.
func [](heap: HeapQueue[T]; i: int64): var T
Accesses the i-th element of heap's internal array. heap[0] is the smallest element.
proc push(heap: var HeapQueue[T]; item: sink T)
Pushes item onto heap, keeping the heap invariant.
proc pop(heap: var HeapQueue[T]): T
Removes and returns the smallest element of heap. Requires a non-empty heap.
proc clear(heap: var HeapQueue[T])
Removes all elements from heap.
proc toHeapQueue(xs: openArray[T]): HeapQueue[T]
Builds a heap from the elements of xs.
iterator items(heap: HeapQueue[T]): var T
Yields each element of heap in its internal (heap-array) order.
func find(heap: HeapQueue[T]; x: T): int64
Linear scan for x; returns its internal index, or -1 if absent.
func contains(heap: HeapQueue[T]; x: T): bool
Whether x is in heap (shortcut for find(heap, x) >= 0).
proc del(heap: var HeapQueue[T]; index: int64)
Removes the element at internal index, keeping the heap invariant.
proc replace(heap: var HeapQueue[T]; item: sink T): T
Pops and returns the smallest element, then pushes item — more efficient than pop + push. Requires a non-empty heap. The returned value may be larger than item.
proc pushpop(heap: var HeapQueue[T]; item: sink T): T
A push(item) immediately followed by a pop(), but faster.