skewheap

NAME

SkewHeap - a self-balancing min heap with O(log n) performance

SYNOPSIS

const SkewHeap = require("skewheap");

const q = new SkewHeap((a, b) => {
  if (a < b) return -1;
  if (b < a) return 1;
  return 0;
});

for (let i = 0; i < 100; ++i) {
  q.put(i);
}

while (!q.is_empty) {
  const item = q.take();
}

DESCRIPTION

A skew heap is a min heap (a priority queue) for which all destructive operations (put, take) are implemented in terms of a single function, merge. Operations on a skew heap have an ammortized performance of O(log n) (in fact, it is slightly better than that). A skew heap's most interesting characteristic is the ability to quickly merge with another skew heap.

METHODS

new

Accepts one parameter, a function taking two arguments, which it compares and returns 1, 0, or -1. Returning -1 or 0 signifies that the first parameter is less than or equal to the second and should be ordered ahead of the second parameter.

size

Returns the number of items in the queue.

is_empty

Returns true if the queue has no items in it.

put

Puts one or more items into the queue. Accepts a variable number of arguments. All arguments must be comparable via the comparison function provided to the constructor.

heap.put(42)
heap.put(1, 2, 3, 4)

take

Returns the next item from the queue. If there are no items in the queue, returns undefined.

drain

Drains all items from the heap and returns them in an array.

merge

Non-destructively merges another heap with this heap, returning a new heap containing all of the items in both heaps.

const new_heap = one_heap.merge(another_heap);

absorb

Destructively absorbs all of the items in another heap. After calling this method, the other heap will be empty.

one_heap.absorb(another_heap);

AUTHOR

Jeff Ober [e-mail]

LICENSE

Copyright 2018 Jeff Ober

Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.