How to sort a slice of ints in Golang?

In Go, slices provide a flexible way to manage sequences of elements. To sort a slice of ints, the sort package offers a few straightforward functions. In this article we will learn How to Sort a Slice of Ints in Golang.

Example

package main
import (
    "fmt"
    "sort"
)

func main() {
    intSlice := []int{42, 23, 16, 15, 8, 4}
    fmt.Println("Before:", intSlice)

    // Sorting in ascending order
    sort.Ints(intSlice)
    fmt.Println("After:", intSlice)
}

Before: [42 23 16 15 8 4]
After: [4 8 15 16 23 42]

Syntax

func Ints(slc []int)                                                              #Sorting with sort.Ints
func IntsAreSorted(slc []int) bool                                   # Check Slice sorting with sort.IntsAreSorted

Sorting with sort.Ints

The sort.Ints function sorts a slice of ints in ascending order, modifying the slice directly.

Syntax

func Ints(slc []int)

Example

Using the earlier intSlice example, we applied sort.Ints to sort the integers in place. The result is an ascending order.

Checking if a Slice is Sorted with sort.IntsAreSorted

If you need to check whether a slice is already sorted in ascending order, you can use sort.IntsAreSorted. This function returns true if the slice is sorted and false otherwise.

Syntax

func IntsAreSorted(slc []int) bool

Example

package main
import (
    "fmt"
    "sort"
)

func main() {
    intSlice := []int{42, 23, 16, 15, 8, 4}

    // Check if the slice is sorted
    fmt.Println("sorted before sorting?:", sort.IntsAreSorted(intSlice))

    // Sort the slice
    sort.Ints(intSlice)

    // Check again
    fmt.Println("sorted after sorting?:", sort.IntsAreSorted(intSlice))
}

sorted before sorting?: false
sorted after sorting?: true

Sorting in Descending Order with sort.Slice

If you want to sort in descending order, you can use sort.Slice with a custom comparison function.

Example

package main
import (
    "fmt"
    "sort"
)

func main() {
    intSlice := []int{42, 23, 16, 15, 8, 4}

    // Sort in descending order
    sort.Slice(intSlice, func(i, j int) bool {
        return intSlice[i] > intSlice[j]
    })

    fmt.Println("descending order:", intSlice)
}

Note: If you are encountering an error indicating that the sort.Slice function is not recognized, it may be due to using an older version of Go that does not support this function. The sort.Slice function was introduced in Go 1.8, so ensure that your Go version is at least 1.8 or higher.