排序算法：Insertion Sort和Merge Sort in GoLang

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最近在学习算法导论，课程上讲了两种排序算法，分别是插入排序法和合并选择法

下面用GO语言实现，不过实现得不够简洁，这位作者的更好http://austingwalters.com/merge-sort-in-go-golang/

package sort//InsertionSort 插入排序 n^2func InsertionSort(arr []int) {if len(arr) < 2 {return}for j := 1; j < len(arr); j++ {key := arr[j]i := j - 1for i >= 0 && arr[i] > key {arr[i+1] = arr[i]i--}arr[i+1] = key}}//MergeSort 合并选择算法 nlgnfunc MergeSort(arr []int) (sorted []int) {n := len(arr)if n == 1 {return arr}    sorted1 := MergeSort(arr[0 : n/2]) sorted2 := MergeSort(arr[n/2:])       return mergeSortedList(sorted1,sorted2)}func mergeSortedList(arr1, arr2 []int) []int {len1 := len(arr1)len2 := len(arr2)var pointer1, pointer2 intresult := make([]int, len1+len2)var index = 0 for (pointer1 < len1) && (pointer2 < len2) {if arr1[pointer1] < arr2[pointer2] {result[index] = arr1[pointer1]            pointer1++} else {result[index] = arr2[pointer2]        pointer2++}index++}//arr1或者arr2被提取完时if pointer1 == len1 {for i := pointer2; i < len2; i++ {result[index] = arr2[i]index++}} else {for i := pointer1; i < len1; i++ {result[index] = arr1[i]index++}}     return result}

觉得实现的不够简洁，修改了一下，采用添加哨兵的方式来减少程序中的判断

//这个版本性能更好，加入了哨兵牌，就可以不用做过顶的检查func mergeSortedList2(arr1, arr2 []int) []int {    var p1, p2 int    length := len(arr1) + len(arr2)    result := make([]int, length)    var arr1M, arr2M []int                arr1M = append(arr1M, arr1...)    arr1M = append(arr1M, math.MaxInt64)     arr2M = append(arr2M, arr2...)    arr2M = append(arr2M, math.MaxInt64)        for index := 0; index < length; index++ {        if arr1M[p1] < arr2M[p2] {            result[index] = arr1M[p1]            p1++        } else {            result[index] = arr2M[p2]            p2++        }    }    return result}

下面是测试代码

package sortimport(    "testing"    "fmt")func TestSort(t *testing.T) {    fmt.Println("开始测试")    arr := []int{10, 7, 1, 5, 11, 3, 100, 250, 110, 13, 0, -88, -7}                    InsertionSort(arr)    fmt.Println(arr)}func TestMergeSort(t *testing.T) {    fmt.Println("开始测试")    arr := []int{10, 7, 1, 5, 11, 3, 100, 250, 110, 13, 0, -88, -7}                       result := MergeSort(arr)    fmt.Println(result)}

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