feature(swift): Reimplement merge_sort and top_k (#898)

* feat: Add swift-collections

* fix: use heap

* refactor: merge

* fix: import HeapModule

codes/swift/chapter_heap/top_k.swift

@@ -4,21 +4,22 @@
  * Author: nuomi1 (nuomi1@qq.com)
  */
 
+import HeapModule
 import utils
 
 /* 基于堆查找数组中最大的 k 个元素 */
 func topKHeap(nums: [Int], k: Int) -> [Int] {
     // 将数组的前 k 个元素入堆
-    var heap = Array(nums.prefix(k))
+    var heap = Heap(nums.prefix(k))
     // 从第 k+1 个元素开始，保持堆的长度为 k
     for i in stride(from: k, to: nums.count, by: 1) {
         // 若当前元素大于堆顶元素，则将堆顶元素出堆、当前元素入堆
-        if nums[i] > heap.first! {
-            heap.removeFirst()
-            heap.insert(nums[i], at: 0)
+        if nums[i] > heap.min()! {
+            _ = heap.removeMin()
+            heap.insert(nums[i])
         }
     }
-    return heap
+    return heap.unordered
 }
 
 @main