I cannot allocate value in slide by using for loop in Go

Question

Hello I am trying to study array in Leetcode.

I know that slide value will be reflected on original array by using array[index] = value.

But this code didn't work what I thought originally.

I cannot use pointer and return because I can only hand function in Leetcode.

Would you kindly check below my code?

I used Quick sort with partition.

Thank you.

https://go.dev/play/p/dNgYqPZCZqK

package main

import "fmt"

func main() {
    nums1 := []int{1, 2, 3, 0, 0, 0}
    nums2 := []int{2, 5, 6}
    merge(nums1, len(nums1), nums2, len(nums2))
    fmt.Println(nums1) //  Expected : [1 2 2 3 5 6] but [1 2 3 0 0 0]
}

func merge(nums1 []int, m int, nums2 []int, n int) {
    count := 0
    nums1 = append(nums1, nums2...)
    nums1 = quicksort(nums1, 0, m+n-1)
    for i := range nums1 {
        if nums1[i] == 0 {
            count++
        }
    }
    nums1 = nums1[count:]

    for j := range nums1 {
        nums1[j] = nums1[j] //self assignment for sure
    }
    fmt.Println(nums1)  // [1 2 2 3 5 6]

}
func quicksort(arr []int, low, high int) []int {
    if low < high {
        arr, p := partition(arr, low, high)
        arr = quicksort(arr, low, p-1)
        arr = quicksort(arr, p+1, high)
    }
    return arr
}

func partition(arr []int, low, high int) ([]int, int) {
    pivot := arr[high]
    i := low
    for j := low; j < high; j++ {
        if arr[j] < pivot {
            arr[i], arr[j] = arr[j], arr[i]
            i++
        }
    }
    arr[i], arr[high] = arr[high], arr[i]
    return arr, i
}

Answer 1

I changed append variable from nums1 to temp. Maybe that made nums1 as copy slide.

So after changing nums1 to temp, later allocate values from temp to nums1.

It works!

https://go.dev/play/p/fU-06ZBWiFA

package main

import "fmt"

func main() {
    nums1 := []int{1, 2, 3, 0, 0, 0}
    nums2 := []int{2, 5, 6}
    merge(nums1, len(nums1), nums2, len(nums2))
    fmt.Println(nums1) //  Expected : [1 2 2 3 5 6] but [1 2 3 0 0 0]
}

func merge(nums1 []int, m int, nums2 []int, n int) {
    count := 0
    temp := append(nums1, nums2...)
    temp = quicksort(temp, 0, m+n-1)
    for i := range temp {
        if temp[i] == 0 {
            count++
        }
    }
    temp = temp[count:]

    for j := range nums1 {
        nums1[j] = temp[j] //self assignment for sure
    }
    fmt.Println(nums1)

}
func quicksort(arr []int, low, high int) []int {
    if low < high {
        arr, p := partition(arr, low, high)
        arr = quicksort(arr, low, p-1)
        arr = quicksort(arr, p+1, high)
    }
    return arr
}

func partition(arr []int, low, high int) ([]int, int) {
    pivot := arr[high]
    i := low
    for j := low; j < high; j++ {
        if arr[j] < pivot {
            arr[i], arr[j] = arr[j], arr[i]
            i++
        }
    }
    arr[i], arr[high] = arr[high], arr[i]
    return arr, i
}