Review Swift codes (#1150)

* feat(swift): review for chapter_computational_complexity

* feat(swift): review for chapter_data_structure

* feat(swift): review for chapter_array_and_linkedlist

* feat(swift): review for chapter_stack_and_queue

* feat(swift): review for chapter_hashing

* feat(swift): review for chapter_tree

* feat(swift): add codes for heap article

* feat(swift): review for chapter_heap

* feat(swift): review for chapter_graph

* feat(swift): review for chapter_searching

* feat(swift): review for chapter_sorting

* feat(swift): review for chapter_divide_and_conquer

* feat(swift): review for chapter_backtracking

* feat(swift): review for chapter_dynamic_programming

* feat(swift): review for chapter_greedy

* feat(swift): review for utils

* feat(swift): update ci tool

* feat(swift): trailing closure

* feat(swift): array init

* feat(swift): map index

codes/swift/chapter_heap/top_k.swift

@@ -12,7 +12,7 @@ func topKHeap(nums: [Int], k: Int) -> [Int] {
     // 初始化一个小顶堆，并将前 k 个元素建堆
     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) {
+    for i in nums.indices.dropFirst(k) {
         // 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.min()! {
             _ = heap.removeMin()