From 4d3128a4a7ee97b2a8a13128c82add47baec60e2 Mon Sep 17 00:00:00 2001 From: machangxin Date: Tue, 13 Dec 2022 14:24:17 +0800 Subject: [PATCH] merge sort using go --- .../chapter_sorting/merge_sort/merge_sort.go | 53 +++++++++++++++++++ .../merge_sort/merge_sort_test.go | 15 ++++++ docs/chapter_sorting/merge_sort.md | 49 ++++++++++++++++- 3 files changed, 116 insertions(+), 1 deletion(-) create mode 100644 codes/go/chapter_sorting/merge_sort/merge_sort.go create mode 100644 codes/go/chapter_sorting/merge_sort/merge_sort_test.go diff --git a/codes/go/chapter_sorting/merge_sort/merge_sort.go b/codes/go/chapter_sorting/merge_sort/merge_sort.go new file mode 100644 index 000000000..b6650a763 --- /dev/null +++ b/codes/go/chapter_sorting/merge_sort/merge_sort.go @@ -0,0 +1,53 @@ +package merge_sort +// File: merge_sort.go +// Created Time: 2022-12-13 +// Author: msk397 (machangxinq@gmail.com) + +/* + 合并左子数组和右子数组 + 左子数组区间 [left, mid] + 右子数组区间 [mid + 1, right] +*/ +func merge(nums []int, left, mid, right int) { + // 初始化辅助数组 借助 copy模块 + tmp := make([]int, right-left+1) + for i := left; i <= right; i++ { + tmp[i-left] = nums[i] + } + // 左子数组的起始索引和结束索引 + left_start, left_end := left-left, mid-left + // 右子数组的起始索引和结束索引 + right_start, right_end := mid+1-left, right-left + // i, j 分别指向左子数组、右子数组的首元素 + i, j := left_start, right_start + // 通过覆盖原数组 nums 来合并左子数组和右子数组 + for k := left; k <= right; k++ { + // 若 “左子数组已全部合并完”，则选取右子数组元素，并且 j++ + if i > left_end { + nums[k] = tmp[j] + j++ + // 否则，若 “右子数组已全部合并完” 或 “左子数组元素 < 右子数组元素”，则选取左子数组元素，并且 i++ + } else if j > right_end || tmp[i] <= tmp[j] { + nums[k] = tmp[i] + i++ + // 否则，若 “左子数组元素 > 右子数组元素”，则选取右子数组元素，并且 j++ + } else { + nums[k] = tmp[j] + j++ + } + } +} + + +func mergeSort(nums []int, left, right int) { + // 终止条件 + if left >= right { + return + } + // 划分阶段 + mid := (left + right) / 2 + mergeSort(nums, left, mid) + mergeSort(nums, mid+1, right) + // 合并阶段 + merge(nums, left, mid, right) +} \ No newline at end of file diff --git a/codes/go/chapter_sorting/merge_sort/merge_sort_test.go b/codes/go/chapter_sorting/merge_sort/merge_sort_test.go new file mode 100644 index 000000000..04abd443b --- /dev/null +++ b/codes/go/chapter_sorting/merge_sort/merge_sort_test.go @@ -0,0 +1,15 @@ +package merge_sort +// File: merge_sort_test.go +// Created Time: 2022-12-13 +// Author: msk397 (machangxinq@gmail.com) + +import ( + "fmt" + "testing" +) + +func TestMergeSort(t *testing.T) { + nums := []int{7, 3, 2, 6, 0, 1, 5, 4} + mergeSort(nums, 0, len(nums)-1) + fmt.Println("归并排序完成后 nums = ", nums) +} diff --git a/docs/chapter_sorting/merge_sort.md b/docs/chapter_sorting/merge_sort.md index 2d67dfd89..b7486bae8 100644 --- a/docs/chapter_sorting/merge_sort.md +++ b/docs/chapter_sorting/merge_sort.md @@ -195,7 +195,54 @@ comments: true === "Go" ```go title="merge_sort.go" - + /* + 合并左子数组和右子数组 + 左子数组区间 [left, mid] + 右子数组区间 [mid + 1, right] + */ + func merge(nums []int, left, mid, right int) { + // 初始化辅助数组 借助 copy模块 + tmp := make([]int, right-left+1) + for i := left; i <= right; i++ { + tmp[i-left] = nums[i] + } + // 左子数组的起始索引和结束索引 + left_start, left_end := left-left, mid-left + // 右子数组的起始索引和结束索引 + right_start, right_end := mid+1-left, right-left + // i, j 分别指向左子数组、右子数组的首元素 + i, j := left_start, right_start + // 通过覆盖原数组 nums 来合并左子数组和右子数组 + for k := left; k <= right; k++ { + // 若 “左子数组已全部合并完”，则选取右子数组元素，并且 j++ + if i > left_end { + nums[k] = tmp[j] + j++ + // 否则，若 “右子数组已全部合并完” 或 “左子数组元素 < 右子数组元素”，则选取左子数组元素，并且 i++ + } else if j > right_end || tmp[i] <= tmp[j] { + nums[k] = tmp[i] + i++ + // 否则，若 “左子数组元素 > 右子数组元素”，则选取右子数组元素，并且 j++ + } else { + nums[k] = tmp[j] + j++ + } + } + } + + /* 归并排序 */ + func mergeSort(nums []int, left, right int) { + // 终止条件 + if left >= right { + return + } + // 划分阶段 + mid := (left + right) / 2 + mergeSort(nums, left, mid) + mergeSort(nums, mid+1, right) + // 合并阶段 + merge(nums, left, mid, right) + } ``` === "JavaScript"