# [Golang] Union of Two Arrays

Find the set of all elements in two arrays, i.e., union of two arrays. This is the continued work of my post yesterday [1], which is intersection of two arrays.

The idea is to convert one array to the data structure of key-value pairs, i.e., hash table. The hash table in Go is built-in map type. Then we check if items of the other array is in the hash table. If not, append the item to the first array, and return the first array after finish.

The following is example of above idea.

```
package main
import (
"fmt"
)
func Union(a, b []int) []int {
m := make(map[int]bool)
for _, item := range a {
m[item] = true
}
for _, item := range b {
if _, ok := m[item]; !ok {
a = append(a, item)
}
}
return a
}
func main() {
var a = []int{1, 2, 3, 4, 5}
var b = []int{2, 3, 5, 7, 11}
fmt.Println(Union(a, b))
}
```

The result will be [1 2 3 4 5 7 11].

Tested on: Go Playground

References:

[1] | [Golang] Intersection of Two Arrays |