Checking Element Presence in Go Slices

In Go, a slice doesn't natively include a method like slice.contains(object) for determining the presence of an element. Instead, a common solution is to iterate through each element to conduct the search.

Alternative Approaches:

Custom Method:

Creating a custom slice.contains() method is a straightforward option, as indicated by Mostafa.

package main

import "fmt"

func main() {
    slice := []int{1, 2, 3}
    if sliceContains(slice, 2) {
        fmt.Println("Contains")
    } else {
        fmt.Println("Not contains")
    }
}

func sliceContains(slice []int, object int) bool {
    for _, v := range slice {
        if v == object {
            return true
        }
    }
    return false
}

Binary Search:

As suggested by mkb, utilizing the sort package's binary search algorithm offers a more efficient approach for large slices.

package main

import (
    "fmt"
    "sort"
)

func main() {
    slice := []int{1, 2, 3}
    sort.Ints(slice)
    index := sort.SearchInts(slice, 2)
    if index != len(slice) {
        fmt.Println("Contains")
    } else {
        fmt.Println("Not contains")
    }
}

Using a Map:

If numerous existence checks are anticipated, using a map as an alternative to a slice provides a more efficient solution.

package main

import (
    "fmt"
    "sync"
)

func main() {
    slice := []int{1, 2, 3}
    m := make(map[int]struct{}, len(slice))
    for _, v := range slice {
        m[v] = struct{}{}
    }
    if _, exists := m[2]; exists {
        fmt.Println("Contains")
    } else {
        fmt.Println("Not contains")
    }
}

In this scenario, a map[string]struct{} is frequently employed for sets due to its optimized internal map type for such values.