golang归并排序

func mergeSort(arr []int, start, end int) {
    if start >= end {
        return
    }
    mid:=(start + end) / 2
    mergeSort(arr, start, mid)
    mergeSort(arr, mid+1, end)
    merge(arr, start, mid, end)
}

func merge(arr []int, start, mid, end int) {
    var tmparr = []int{}
    var s1, s2 = start, mid+1
    for s1<= mid && s2<= end{
        if arr[s1] > arr[s2] {
            tmparr = append(tmparr, arr[s2])
            s2++
        } else {
            tmparr = append(tmparr, arr[s1])
            s1++
        }
    }
    if s1<=mid {
        tmparr = append(tmparr, arr[s1: mid+1]...)
    }
    if s2<=end {
        tmparr = append(tmparr, arr[s2: end+1]...)
    }
    for pos,item:=range tmparr{
        arr[start + pos] = item
    }
}


var a=[]int{3,4,0,1,5,6,7,8}

func main() {
    mergeSort(a, 0, len(a) - 1)
    fmt.Println(a)
}

知识点是go slice区间：

slice[i:j]表示以i ，到j索引结束, 截取原数组或者切片，创建而成的新切片，新切片的值包含原切片的i索引，但是不包含j索引。左闭右开。

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