what is wrong with go language code converted from equivalent python?-CodePudding

I am new to Go Language and trying to learn it by doing. tried with MergeSort but some how I am missing something and result is not as expected. I am pretty sure it has something to do with slices I am using.

converted equivalent python code to go python works but go code missed something (in terms of my understanding to slice may be)

working Python Code

def mergeSort(arr):
    if len(arr) > 1:
 
         # Finding the mid of the array
        mid = len(arr)//2
 
        # Dividing the array elements
        L = arr[:mid]
 
        # into 2 halves
        R = arr[mid:]
 
        # Sorting the first half
        mergeSort(L)
 
        # Sorting the second half
        mergeSort(R)
 
        i = j = k = 0
 
        # Copy data to temp arrays L[] and R[]
        while i < len(L) and j < len(R):
            if L[i] < R[j]:
                arr[k] = L[i]
                i  = 1
            else:
                arr[k] = R[j]
                j  = 1
            k  = 1
 
        # Checking if any element was left
        while i < len(L):
            arr[k] = L[i]
            i  = 1
            k  = 1
 
        while j < len(R):
            arr[k] = R[j]
            j  = 1
            k  = 1
 
# Code to print the list
 
 
def printList(arr):
    for i in range(len(arr)):
        print(arr[i], end=" ")
    print()

# Driver Code
arr = [457, 4, 0, 500, -8, 6, 5, -20, -93, 50, 5, 1, 6, 10, 54, 7, 13, 10, -5, 50, 500, 8, 4, -1, -99, 5, 0, 0, -899]
printList(mergeSort(arr))

Converted equivalent Go Code

package main
import "fmt"

func main() {
    intArr := []int{457, 4, 0, 500, -8, 6, 5, -20, -93, 50, 5, 1, 6, 10, 54, 7, 13, 10, -5, 50, 500, 8, 4, -1, -99, 5, 0, 0, -899}
    fmt.Println(mergeSort(intArr))
}

func mergeSort(arr []int) []int {
    if len(arr) > 1 {

        // Finding the mid of the array
        mid := int(len(arr) / 2)

        // Dividing the array elements
        L := arr[:mid]

        // into 2 halves
        R := arr[mid:]

        // Sorting the first half
        mergeSort(L)

        // Sorting the second half
        mergeSort(R)

        i, j, k := 0, 0, 0

        // Copy data to temp arrays L[] and R[]
        for i < len(L) && j < len(R) {
            if L[i] < R[j] {
                arr[k] = L[i]
                i  
            } else {
                arr[k] = R[j]
                j  
            }
            k  
        }

        // Checking if any element was left
        for i < len(L) {
            arr[k] = L[i]
            i  
            k  
        }

        for j < len(R) {
            arr[k] = R[j]
            j  
            k  
        }
    }
    return arr
}

but output is from Go code

[-899 -899 -899 -899 -899 -899 -899 -899 -899 -899 -899 -899 -899 -899 -899 -899 -899 -899 -899 -899 -899 -899 -899 -899 -899 -899 -899 -899 -899]

CodePudding user response：

Array slicing does not allocate new arrays in go. L, R and arr refers to the same underlying array. You can use "copy" to deep clone the slice:

    func mergeSort(arr []int) []int {
        if len(arr) > 1 {        

            // Finding the mid of the array
            mid := int(len(arr) / 2)        

            // Dividing the array elements
            L := make([]int, mid)
            copy(L, arr[:mid])        

            // into 2 halves
            R := make([]int, len(arr)-mid)
            copy(R, arr[mid:])        

            // Sorting the first half
            mergeSort(L)        

            // Sorting the second half
            mergeSort(R)        

            i, j, k := 0, 0, 0        

            // Copy data to temp arrays L[] and R[]
            for i < len(L) && j < len(R) {
                if L[i] < R[j] {
                    arr[k] = L[i]
                    i  
                } else {
                    arr[k] = R[j]
                    j  
                }
                k  
            }        

            // Checking if any element was left
            for i < len(L) {
                arr[k] = L[i]
                i  
                k  
            }        

            for j < len(R) {
                arr[k] = R[j]
                j  
                k  
            }
        }
        return arr
    }