jacks205 / swift-priorityqueue

Binary heap implementation in Swift

Swift-PriorityQueue

When included as a framework, import it as any other framework:

import PriorityQueue

The priority queue is defined as a generic and initialized with a comparison callback, like PriorityQueue<T>((T, T) -> Bool). For example, it can operate on characters like this:

var characters = PriorityQueue<Character>(<)
characters.push("C")
characters.push("B")
characters.push("A")

println("Characters:")
for p in characters {
    println(" * \(p)")
}
println()

This would print:

 * A
 * B
 * C

A more real-world use-case would operate on structs or classes, like this:

struct Node {
    let priority: Int
}

var nodes = PriorityQueue<Node>({ $0.priority < $1.priority })
nodes.push(Node(priority: 4))
nodes.push(Node(priority: 5))
nodes.push(Node(priority: 3))
nodes.push(Node(priority: 1))

println("Nodes:")
for node in nodes {
    println(" * Node(priority: \(node.priority))")
}
println()

This would print:

Nodes:
* Node(priority: 1)
* Node(priority: 3)
* Node(priority: 4)
* Node(priority: 5)

Removing items

var ints = PriorityQueue<Int>(<)
ints.push(3)
ints.remove(3)  // Returns 3
ints.remove(3)  // Returns nil

Inspecting the heap

ints.push(5)
ints.push(4)
ints.heap  // Returns [4, 5]

Alternatives

• CFBinaryHeap (once CFunctionPointer becomes available)
• Swift-DataStructures/MinPQ

Development

Playground

Rebuild this playground with the following command:

rm -rf README.playground/
playground README.md --platform ios