Golang:作为参考问题传入Slice

Question

我正在尝试编写一个计算数组中的反转的程序,但由于引用问题,我的数组没有正确排序,因此即使我认为切片在Golang中通过引用传递,也会弄乱我的计数.

这是我的代码:

package main

import (
    "fmt"
)

func InversionCount(a []int) int {
    if len(a) <= 1 {
        return 0
    }
    mid := len(a) / 2
    left := a[:mid]
    right := a[mid:]
    leftCount := InversionCount(left) //not being sorted properly due to reference issues 
    rightCount := InversionCount(right) //not being sorted properly due to reference issues

    res := make([]int, 0, len(right)+len(left)) //temp slice to hold the sorted left side and right side

    iCount := mergeCount(left, right, &res)

    a = res        //assigns the original slice with the temp slice values
    fmt.Println(a) //a in the end is not sorted properly for most cases 
    return iCount + leftCount + rightCount
}

    func mergeCount(left, right []int, res *[]int) int {
        count := 0

        for len(left) > 0 || len(right) > 0 {
            if len(left) == 0 {
                *res = append(*res, right...)
                break
            }
            if len(right) == 0 {
                *res = append(*res, left...)
                break
            }
        if left[0] <= right[0] {
            *res = append(*res, left[0])
            left = left[1:]
        } else { //Inversion has been found
            count += len(left)
            *res = append(*res, right[0])
            right = right[1:]
        }
    }

    return count
}

func main() {
    test := []int{4,2,3,1,5}
    fmt.Print(InversionCount(test))
}

什么是解决这个问题的最佳方法？我试图res通过强制mergeCount函数接受数组的引用来做类似于我对数组的操作,但它看起来非常混乱,它会给我错误.

Answer 1

您必须将指针传递给切片,如:

func InversionCount(a *[]int) int {
    if len(*a) <= 1 {
        return 0
    }
    mid := len(*a) / 2
    left := (*a)[:mid]
    right := (*a)[mid:]
    leftCount := InversionCount(&left)   //not being sorted properly due to reference issues
    rightCount := InversionCount(&right) //not being sorted properly due to reference issues

    res := make([]int, 0, len(right)+len(left)) //temp slice to hold the sorted left side and right side

    iCount := mergeCount(left, right, &res)

    *a = res
    fmt.Println(a) //a in the end is not sorted properly for most cases
    return iCount + leftCount + rightCount
}

playground

或者使用copy和更改a = res来copy(a, res).

playground