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std.container.binaryheap
This module provides a BinaryHeap (aka priority queue)
adaptor that makes a binary heap out of any user-provided random-access range.
This module is a submodule of std.container.
Source std/container/binaryheap.d
License:
Distributed under the Boost Software License, Version 1.0.
(See accompanying file LICENSE_1_0.txt or copy at boost.org/LICENSE_1_0.txt).
Authors:
Examples:
import std.algorithm.comparison : equal; import std.range : take; auto maxHeap = heapify([4, 7, 3, 1, 5]); assert(maxHeap.take(3).equal([7, 5, 4])); auto minHeap = heapify!"a > b"([4, 7, 3, 1, 5]); assert(minHeap.take(3).equal([1, 3, 4]));
- struct
BinaryHeap
(Store, alias less = "a < b") if (isRandomAccessRange!Store || isRandomAccessRange!(typeof(Store.init[]))); - Implements a binary heap container on top of a given random-access range type (usually T[]) or a random-access container type (usually Array!T). The documentation of
BinaryHeap
will refer to the underlying range or container as the store of the heap.The binary heap induces structure over the underlying store such that accessing the largest element (by using the front property) is a Ο(1) operation and extracting it (by using the removeFront() method) is done fast in Ο(log n) time. If less is the less-than operator, which is the default option, thenBinaryHeap
defines a so-called max-heap that optimizes extraction of the largest elements. To define a min-heap, instantiate BinaryHeap with "a > b" as its predicate. Simply extracting elements from aBinaryHeap
container is tantamount to lazily fetching elements of Store in descending order. Extracting elements from theBinaryHeap
to completion leaves the underlying store sorted in ascending order but, again, yields elements in descending order. If Store is a range, theBinaryHeap
cannot grow beyond the size of that range. If Store is a container that supports insertBack, theBinaryHeap
may grow by adding elements to the container.Examples:Example from "Introduction to Algorithms" Cormen et al, p 146import std.algorithm.comparison : equal; int[] a = [ 4, 1, 3, 2, 16, 9, 10, 14, 8, 7 ]; auto h = heapify(a); // largest element writeln(h.front); // 16 // a has the heap property assert(equal(a, [ 16, 14, 10, 8, 7, 9, 3, 2, 4, 1 ]));
Examples:BinaryHeap
implements the standard input range interface, allowing lazy iteration of the underlying range in descending order.import std.algorithm.comparison : equal; import std.range : take; int[] a = [4, 1, 3, 2, 16, 9, 10, 14, 8, 7]; auto top5 = heapify(a).take(5); assert(top5.equal([16, 14, 10, 9, 8]));
- this(Store
s
, size_tinitialSize
= size_t.max); - Converts the store
s
into a heap. IfinitialSize
is specified, only the firstinitialSize
elements ins
are transformed into a heap, after which the heap can grow up to r.length (if Store is a range) or indefinitely (if Store is a container with insertBack). Performs Ο(min(r.length, initialSize)) evaluations of less. - void
acquire
(Stores
, size_tinitialSize
= size_t.max); - Takes ownership of a store. After this, manipulating
s
may make the heap work incorrectly. - void
assume
(Stores
, size_tinitialSize
= size_t.max); - Takes ownership of a store assuming it already was organized as a heap.
- auto
release
(); - Clears the heap. Returns the portion of the store from 0 up to length, which satisfies the heap property.
- @property bool
empty
(); - Returns true if the heap is empty, false otherwise.
- @property BinaryHeap
dup
(); - Returns a duplicate of the heap. The
dup
method is available only if the underlying store supports it. - @property size_t
length
(); - Returns the length of the heap.
- @property size_t
capacity
(); - Returns the capacity of the heap, which is the length of the underlying store (if the store is a range) or the capacity of the underlying store (if the store is a container).
- @property ElementType!Store
front
(); - Returns a copy of the front of the heap, which is the largest element according to less.
- void
clear
(); - Clears the heap by detaching it from the underlying store.
- size_t
insert
(ElementType!Storevalue
); - Inserts
value
into the store. If the underlying store is a range and length == capacity, throws an exception. - void
removeFront
();
aliaspopFront
= removeFront; - Removes the largest element from the heap.
- ElementType!Store
removeAny
(); - Removes the largest element from the heap and returns a copy of it. The element still resides in the heap's store. For performance reasons you may want to use removeFront with heaps of objects that are expensive to copy.
- void
replaceFront
(ElementType!Storevalue
); - Replaces the largest element in the store with
value
. - bool
conditionalInsert
(ElementType!Storevalue
); - If the heap has room to grow, inserts
value
into the store and returns true. Otherwise, if less(value, front), calls replaceFront(value) and returns again true. Otherwise, leaves the heap unaffected and returns false. This method is useful in scenarios where the smallest k elements of a set of candidates must be collected. - bool
conditionalSwap
(ref ElementType!Storevalue
); - Swapping is allowed if the heap is full. If less(value, front), the method exchanges store.front and value and returns true. Otherwise, it leaves the heap unaffected and returns false.
- BinaryHeap!(Store, less)
heapify
(alias less = "a < b", Store)(Stores
, size_tinitialSize
= size_t.max); - Convenience function that returns a BinaryHeap!Store object initialized with
s
andinitialSize
.Examples:import std.conv : to; import std.range.primitives; { // example from "Introduction to Algorithms" Cormen et al., p 146 int[] a = [ 4, 1, 3, 2, 16, 9, 10, 14, 8, 7 ]; auto h = heapify(a); h = heapify!"a < b"(a); writeln(h.front); // 16 writeln(a); // [16, 14, 10, 8, 7, 9, 3, 2, 4, 1] auto witness = [ 16, 14, 10, 9, 8, 7, 4, 3, 2, 1 ]; for (; !h.empty; h.removeFront(), witness.popFront()) { assert(!witness.empty); writeln(witness.front); // h.front } assert(witness.empty); } { int[] a = [ 4, 1, 3, 2, 16, 9, 10, 14, 8, 7 ]; int[] b = new int[a.length]; BinaryHeap!(int[]) h = BinaryHeap!(int[])(b, 0); foreach (e; a) { h.insert(e); } writeln(b); // [16, 14, 10, 8, 7, 3, 9, 1, 4, 2] }
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