迭代版排序
```go
package main
import (
"fmt"
)
func main() {
var arr = []int{6, 5, 3, 1, 8, 7, 2, 4, 9}
fmt.Println(arr)
fmt.Println(MergeSort(arr))
}
func MergeSort(arr []int) []int {
var alen = len(arr)
var ns = make([]int, alen, alen)
var tmp = &arr
var stmp = &ns
for add := 1; add < alen; add *= 2 {
fmt.Println(add)
var start1 = 0
var start2 = 0
ik := 0
for start1 = 0; start1 < alen; start1 = start1 + add {
start2 = start1 + add
var end1 = start1 + add
var end2 = start2 + add
for start1 < end1 && start2 < end2 && start1 < alen && start2 < alen {
if (*tmp)[start1] < (*tmp)[start2] {
(*stmp)[ik] = (*tmp)[start1]
start1++
} else {
(*stmp)[ik] = (*tmp)[start2]
start2++
}
ik++
fmt.Println(*stmp)
}
for start1 < end1 && start1 < alen {
(*stmp)[ik] = (*tmp)[start1]
start1++
ik++
fmt.Println(*stmp)
}
for start2 < end2 && start2 < alen {
(*stmp)[ik] = (*tmp)[start2]
start2++
ik++
fmt.Println(*stmp)
}
}
tmp, stmp = stmp, tmp
for index, _ := range *stmp {
(*stmp)[index] = 0
}
}
return (*tmp)
}
```
感觉写不是太好，有没有什么办法直接复制指定长度内存？请大神回复
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