Documentation
¶
Overview ¶
Package heap provides heap operations for a type A and a comparison function Less. A heap is a tree with the property that each node is the minimum-valued node in its subtree.
The minimum element in the tree is the root, at index 0.
This provides a min-heap with the following invariants (established after Init has been called or if the data is empty or sorted):
!Less(h[j], h[i]) for 0 <= i < len(h) and j = 2*i+1 or 2*i+2 and j < len(h)
A heap is a common way to implement a priority queue. To build a priority queue, use the (negative) priority as the ordering for the Less method, so Push adds items while Pop removes the highest-priority item from the queue. The Examples include such an implementation; the file example_pq_test.go has the complete source.
Example (IntHeap) ¶
This example inserts several ints into an IntHeap, checks the minimum, and removes them in order of priority.
package main
import (
"fmt"
"github.com/ncw/gotemplate/heap"
)
func main() {
h := &heap.Heap{2, 1, 5}
h.Init()
h.Push(3)
fmt.Printf("minimum: %d\n", (*h)[0])
for len(*h) > 0 {
fmt.Printf("%d ", h.Pop())
}
}
Output: minimum: 1 1 2 3 5
Index ¶
Examples ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
Types ¶
type A ¶
type A int
An A is the element in the slice []A we are keeping as a heap
template type Heap(A, Less)
type Heap ¶
type Heap []A
Heap stored in an slice
func (*Heap) Fix ¶
Fix re-establishes the heap ordering after the element at index i has changed its value. Changing the value of the element at index i and then calling Fix is equivalent to, but less expensive than, calling h.Remove(i) followed by a Push of the new value. The complexity is O(log(n)) where n = len(h).
func (*Heap) Init ¶
func (h *Heap) Init()
Init is compulsory before any of the heap operations can be used. Init is idempotent with respect to the heap invariants and may be called whenever the heap invariants may have been invalidated. Its complexity is O(n) where n = len(h).
func (*Heap) Pop ¶
Pop removes the minimum element (according to Less) from the heap and returns it. The complexity is O(log(n)) where n = len(h). It is equivalent to h.Remove(0).
Source Files