[Swift]自定义数据结构：优先队列PriorityQueue

 1 public struct PriorityQueue<T: Comparable> {    
 2     fileprivate var heap = [T]()
 3     private let ordered: (T,T) -> Bool
 4     
 5     //创建具有给定顺序的新PriorityQueue。
 6     //order：true:降序 | false：升序
 7     //StartingValues:用于初始化PriorityQueue的元素数组。
 8     public init(_ ascending: Bool = false,_ startingValues: [T] = []) {
 9         self.init(order: ascending ? { $0 > $1 } : { $0 < $1 },startingValues: startingValues)
10     }
11     
12     public init(order: @escaping (T,T) -> Bool,startingValues: [T] = []) {
13         ordered = order        
14         //堆构造
15         heap = startingValues
16         var i = heap.count/2 - 1
17         while i >= 0 {
18             sink(i)
19             i -= 1
20         }
21     }
22     
23     //优先级队列存储了多少个元素
24     public var count: Int { return heap.count }
25     
26     //如果且仅当优先级队列为空时为true
27     public var isEmpty: Bool { return heap.isEmpty }
28     
29     // 在优先级队列中添加新元素,复杂度：O(lg n)
30     // element: 要插入优先级队列的元素.
31     public mutating func push(_ element: T) {
32         heap.append(element)
33         swim(heap.count - 1)
34     }
35     
36     //移除并返回具有最高优先级的元素（如果升序，则为最低优先级）。复杂度： O(lg n)
37     //returns:优先级队列中优先级最高的元素，如果优先级队列为空，则为零。
38     public mutating func pop() -> T? {        
39         if heap.isEmpty { return nil }
40         //增加了Swift 2兼容性
41         if heap.count == 1 { return heap.removeFirst() } 
42         //以便不使用同一位置的两个实例调用swap()
43         heap.swapAt(0,heap.count - 1)
44         let temp = heap.removeLast()
45         sink(0)        
46         return temp
47     }
48     
49     private mutating func sink(_ index: Int) {
50         var index = index
51         while 2 * index + 1 < heap.count {            
52             var j = 2 * index + 1            
53             if j < (heap.count - 1) && ordered(heap[j],heap[j + 1]) { j += 1 }
54             if !ordered(heap[index],heap[j]) { break }            
55             heap.swapAt(index,j)
56             index = j
57         }
58     }
59     
60     private mutating func swim(_ index: Int) {
61         var index = index
62         while index > 0 && ordered(heap[(index - 1) / 2],heap[index]) {
63             heap.swapAt((index - 1) / 2,index)
64             index = (index - 1) / 2
65         }
66     }
67 }

 1 var pq: PriorityQueue<Int> = PriorityQueue<Int>(false,[Int]())
 2 pq.push(9)
 3 pq.push(8)
 4 pq.push(7)
 5 pq.push(6)
 6 pq.push(5)
 7 pq.push(4)
 8 pq.push(3)
 9 pq.push(2)
10 pq.push(1)
11 pq.push(0)
12 dump(pq)
13 /*
14 ? prog.PriorityQueue<Swift.Int>
15   ? heap: 10 elements
16     - 9
17     - 8
18     - 7
19     - 6
20     - 5
21     - 4
22     - 3
23     - 2
24     - 1
25     - 0
26   - ordered: (Function)
27 */

 1 var pq: PriorityQueue<Int> = PriorityQueue<Int>(true,[Int]())
 2 pq.push(9)
 3 pq.push(8)
 4 pq.push(7)
 5 pq.push(6)
 6 pq.push(5)
 7 pq.push(4)
 8 pq.push(3)
 9 pq.push(2)
10 pq.push(1)
11 pq.push(0)
12 dump(pq)
13 /*
14 ? prog.PriorityQueue<Swift.Int>
15   ? heap: 10 elements
16     - 0
17     - 1
18     - 4
19     - 3
20     - 2
21     - 8
22     - 5
23     - 9
24     - 6
25     - 7
26   - ordered: (Function)
27 */

 1 var pq: PriorityQueue<Int> = PriorityQueue<Int>(false,[Int]())
 2 pq.push(0)
 3 pq.push(1)
 4 pq.push(2)
 5 pq.push(3)
 6 pq.push(4)
 7 pq.push(5)
 8 pq.push(6)
 9 pq.push(7)
10 pq.push(8)
11 pq.push(9)
12 dump(pq)
13 /*
14 ? prog.PriorityQueue<Swift.Int>
15   ? heap: 10 elements
16     - 9
17     - 8
18     - 5
19     - 6
20     - 7
21     - 1
22     - 4
23     - 0
24     - 3
25     - 2
26   - ordered: (Function)
27 */

 1 var pq: PriorityQueue<Int> = PriorityQueue<Int>(true,[Int]())
 2 pq.push(0)
 3 pq.push(1)
 4 pq.push(2)
 5 pq.push(3)
 6 pq.push(4)
 7 pq.push(5)
 8 pq.push(6)
 9 pq.push(7)
10 pq.push(8)
11 pq.push(9)
12 dump(pq)
13 /*
14 ? prog.PriorityQueue<Swift.Int>
15   ? heap: 10 elements
16     - 0
17     - 1
18     - 2
19     - 3
20     - 4
21     - 5
22     - 6
23     - 7
24     - 8
25     - 9
26   - ordered: (Function)
27 */