xinyin025/hello-algo
1
0
Fork 0
mirror of https://github.com/krahets/hello-algo.git synced 2026-07-12 07:26:07 +00:00
Code Issues Packages Projects Releases Wiki Activity

Review Swift codes (#1150)

Browse Source 
* 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
This commit is contained in:
nuomi1
2024-03-20 21:15:39 +08:00
committed by GitHub
parent 300a781fab
commit 7359a7cb4b
55 changed files with 293 additions and 224 deletions
Download Patch File Download Diff File Expand all files Collapse all files
codes/swift/chapter_sorting/bubble_sort.swift
+6 -10
View File
@@ -7,14 +7,12 @@
/* 冒泡排序 */
func bubbleSort(nums: inout [Int]) {
// 外循环：未排序区间为 [0, i]
for i in stride(from: nums.count - 1, to: 0, by: -1) {
for i in nums.indices.dropFirst().reversed() {
// 内循环：将未排序区间 [0, i] 中的最大元素交换至该区间的最右端
for j in stride(from: 0, to: i, by: 1) {
for j in 0 ..< i {
if nums[j] > nums[j + 1] {
// 交换 nums[j] 与 nums[j + 1]
let tmp = nums[j]
nums[j] = nums[j + 1]
nums[j + 1] = tmp
nums.swapAt(j, j + 1)
}
}
}
@@ -23,14 +21,12 @@ func bubbleSort(nums: inout [Int]) {
/* 冒泡排序（标志优化）*/
func bubbleSortWithFlag(nums: inout [Int]) {
// 外循环：未排序区间为 [0, i]
for i in stride(from: nums.count - 1, to: 0, by: -1) {
for i in nums.indices.dropFirst().reversed() {
var flag = false // 初始化标志位
for j in stride(from: 0, to: i, by: 1) {
for j in 0 ..< i {
if nums[j] > nums[j + 1] {
// 交换 nums[j] 与 nums[j + 1]
let tmp = nums[j]
nums[j] = nums[j + 1]
nums[j + 1] = tmp
nums.swapAt(j, j + 1)
flag = true // 记录交换元素
}
}
codes/swift/chapter_sorting/bucket_sort.swift
+1 -1
View File
@@ -26,7 +26,7 @@ func bucketSort(nums: inout [Double]) {
for bucket in buckets {
for num in bucket {
nums[i] = num
nums.formIndex(after: &i)
i += 1
}
}
}
codes/swift/chapter_sorting/counting_sort.swift
+5 -5
View File
@@ -17,8 +17,8 @@ func countingSortNaive(nums: inout [Int]) {
}
// 3. 遍历 counter ，将各元素填入原数组 nums
var i = 0
for num in stride(from: 0, to: m + 1, by: 1) {
for _ in stride(from: 0, to: counter[num], by: 1) {
for num in 0 ..< m + 1 {
for _ in 0 ..< counter[num] {
nums[i] = num
i += 1
}
@@ -38,19 +38,19 @@ func countingSort(nums: inout [Int]) {
}
// 3. 求 counter 的前缀和，将“出现次数”转换为“尾索引”
// 即 counter[num]-1 是 num 在 res 中最后一次出现的索引
for i in stride(from: 0, to: m, by: 1) {
for i in 0 ..< m {
counter[i + 1] += counter[i]
}
// 4. 倒序遍历 nums ，将各元素填入结果数组 res
// 初始化数组 res 用于记录结果
var res = Array(repeating: 0, count: nums.count)
for i in stride(from: nums.count - 1, through: 0, by: -1) {
for i in nums.indices.reversed() {
let num = nums[i]
res[counter[num] - 1] = num // 将 num 放置到对应索引处
counter[num] -= 1 // 令前缀和自减 1 ，得到下次放置 num 的索引
}
// 使用结果数组 res 覆盖原数组 nums
for i in stride(from: 0, to: nums.count, by: 1) {
for i in nums.indices {
nums[i] = res[i]
}
}
codes/swift/chapter_sorting/heap_sort.swift
+1 -1
View File
@@ -36,7 +36,7 @@ func heapSort(nums: inout [Int]) {
siftDown(nums: &nums, n: nums.count, i: i)
}
// 从堆中提取最大元素，循环 n-1 轮
for i in stride(from: nums.count - 1, to: 0, by: -1) {
for i in nums.indices.dropFirst().reversed() {
// 交换根节点与最右叶节点（交换首元素与尾元素）
nums.swapAt(0, i)
// 以根节点为起点，从顶至底进行堆化
codes/swift/chapter_sorting/insertion_sort.swift
+1 -1
View File
@@ -7,7 +7,7 @@
/* 插入排序 */
func insertionSort(nums: inout [Int]) {
// 外循环：已排序区间为 [0, i-1]
for i in stride(from: 1, to: nums.count, by: 1) {
for i in nums.indices.dropFirst() {
let base = nums[i]
var j = i - 1
// 内循环：将 base 插入到已排序区间 [0, i-1] 中的正确位置
codes/swift/chapter_sorting/merge_sort.swift
+2 -3
View File
@@ -16,12 +16,11 @@ func merge(nums: inout [Int], left: Int, mid: Int, right: Int) {
if nums[i] <= nums[j] {
tmp[k] = nums[i]
i += 1
k += 1
} else {
tmp[k] = nums[j]
j += 1
k += 1
}
k += 1
}
// 将左子数组和右子数组的剩余元素复制到临时数组中
while i <= mid {
@@ -60,7 +59,7 @@ enum MergeSort {
static func main() {
/* 归并排序 */
var nums = [7, 3, 2, 6, 0, 1, 5, 4]
mergeSort(nums: &nums, left: 0, right: nums.count - 1)
mergeSort(nums: &nums, left: nums.startIndex, right: nums.endIndex - 1)
print("归并排序完成后 nums = \(nums)")
}
}
codes/swift/chapter_sorting/quick_sort.swift
+9 -18
View File
@@ -4,13 +4,6 @@
* Author: nuomi1 (nuomi1@qq.com)
*/
/* 元素交换 */
func swap(nums: inout [Int], i: Int, j: Int) {
let tmp = nums[i]
nums[i] = nums[j]
nums[j] = tmp
}
/* 快速排序类 */
/* 哨兵划分 */
func partition(nums: inout [Int], left: Int, right: Int) -> Int {
@@ -24,9 +17,9 @@ func partition(nums: inout [Int], left: Int, right: Int) -> Int {
while i < j, nums[i] <= nums[left] {
i += 1 // 从左向右找首个大于基准数的元素
}
swap(nums: &nums, i: i, j: j) // 交换这两个元素
nums.swapAt(i, j) // 交换这两个元素
}
swap(nums: &nums, i: i, j: left) // 将基准数交换至两子数组的分界线
nums.swapAt(i, left) // 将基准数交换至两子数组的分界线
return i // 返回基准数的索引
}
@@ -43,7 +36,6 @@ func quickSort(nums: inout [Int], left: Int, right: Int) {
quickSort(nums: &nums, left: pivot + 1, right: right)
}
/* 快速排序类（中位基准数优化） */
/* 选取三个候选元素的中位数 */
func medianThree(nums: [Int], left: Int, mid: Int, right: Int) -> Int {
@@ -51,12 +43,12 @@ func medianThree(nums: [Int], left: Int, mid: Int, right: Int) -> Int {
let m = nums[mid]
let r = nums[right]
if (l <= m && m <= r) || (r <= m && m <= l) {
return mid; // m 在 l 和 r 之间
return mid // m 在 l 和 r 之间
}
if (m <= l && l <= r) || (r <= l && l <= m) {
return left; // l 在 m 和 r 之间
return left // l 在 m 和 r 之间
}
return right;
return right
}
/* 哨兵划分（三数取中值） */
@@ -64,7 +56,7 @@ func partitionMedian(nums: inout [Int], left: Int, right: Int) -> Int {
// 选取三个候选元素的中位数
let med = medianThree(nums: nums, left: left, mid: (left + right) / 2, right: right)
// 将中位数交换至数组最左端
swap(nums: &nums, i: left, j: med)
nums.swapAt(left, med)
return partition(nums: &nums, left: left, right: right)
}
@@ -81,7 +73,6 @@ func quickSortMedian(nums: inout [Int], left: Int, right: Int) {
quickSortMedian(nums: &nums, left: pivot + 1, right: right)
}
/* 快速排序（尾递归优化） */
func quickSortTailCall(nums: inout [Int], left: Int, right: Int) {
var left = left
@@ -107,17 +98,17 @@ enum QuickSort {
static func main() {
/* 快速排序 */
var nums = [2, 4, 1, 0, 3, 5]
quickSort(nums: &nums, left: 0, right: nums.count - 1)
quickSort(nums: &nums, left: nums.startIndex, right: nums.endIndex - 1)
print("快速排序完成后 nums = \(nums)")
/* 快速排序（中位基准数优化） */
var nums1 = [2, 4, 1, 0, 3, 5]
quickSortMedian(nums: &nums1, left: 0, right: nums1.count - 1)
quickSortMedian(nums: &nums1, left: nums1.startIndex, right: nums1.endIndex - 1)
print("快速排序（中位基准数优化）完成后 nums1 = \(nums1)")
/* 快速排序（尾递归优化） */
var nums2 = [2, 4, 1, 0, 3, 5]
quickSortTailCall(nums: &nums2, left: 0, right: nums2.count - 1)
quickSortTailCall(nums: &nums2, left: nums2.startIndex, right: nums2.endIndex - 1)
print("快速排序（尾递归优化）完成后 nums2 = \(nums2)")
}
}
codes/swift/chapter_sorting/radix_sort.swift
+14 -5
View File
@@ -14,7 +14,6 @@ func digit(num: Int, exp: Int) -> Int {
func countingSortDigit(nums: inout [Int], exp: Int) {
// 十进制的位范围为 0~9 ，因此需要长度为 10 的桶数组
var counter = Array(repeating: 0, count: 10)
let n = nums.count
// 统计 0~9 各数字的出现次数
for i in nums.indices {
let d = digit(num: nums[i], exp: exp) // 获取 nums[i] 第 k 位，记为 d
@@ -25,8 +24,8 @@ func countingSortDigit(nums: inout [Int], exp: Int) {
counter[i] += counter[i - 1]
}
// 倒序遍历，根据桶内统计结果，将各元素填入 res
var res = Array(repeating: 0, count: n)
for i in stride(from: n - 1, through: 0, by: -1) {
var res = Array(repeating: 0, count: nums.count)
for i in nums.indices.reversed() {
let d = digit(num: nums[i], exp: exp)
let j = counter[d] - 1 // 获取 d 在数组中的索引 j
res[j] = nums[i] // 将当前元素填入索引 j
@@ -62,8 +61,18 @@ enum RadixSort {
/* Driver Code */
static func main() {
// 基数排序
var nums = [10546151, 35663510, 42865989, 34862445, 81883077,
88906420, 72429244, 30524779, 82060337, 63832996]
var nums = [
10_546_151,
35_663_510,
42_865_989,
34_862_445,
81_883_077,
88_906_420,
72_429_244,
30_524_779,
82_060_337,
63_832_996,
]
radixSort(nums: &nums)
print("基数排序完成后 nums = \(nums)")
}