# How to Remove Duplicates in an Array in Golang

## The challenge

Remove the left-most duplicates from a list of integers and return the result.

```
// Remove the 3's at indices 0 and 3
// followed by removing a 4 at index 1
solve([3, 4, 4, 3, 6, 3]); // => [4, 6, 3]
```

## The solution in Golang

Option 1:

```
package solution
func Solve(arr []int) (res []int) {
visited := map[int]bool{}
for i := len(arr) - 1; i >= 0; i-- {
n := arr[i]
if visited[n] { continue }
visited[n] = true
res = append([]int{n}, res...)
}
return
}
```

Option 2:

```
package solution
func Solve(arr []int) []int {
counts := make(map[int]bool)
for _,x := range arr {
counts[x]=true
}
result := make([]int,len(counts))
j := len(result)-1
for i := len(arr)-1; i>=0; i-- {
if counts[arr[i]] {
counts[arr[i]] = false;
result[j] = arr[i]
j--
}
}
return result
}
```

Option 3:

```
package solution
func Solve(a []int) (r[]int) {
m:=map[int]int{}
for _,v:=range a{ m[v]++ }
for _,v:=range a{
if m[v]==1{
r=append(r,v)
}
m[v]--
}
return
}
```

## Test cases to validate our solution

```
package our_test
import (
. "github.com/onsi/ginkgo"
. "github.com/onsi/gomega"
. "codewarrior/kata"
)
func dotest(arr , exp []int) {
var ans = Solve(arr)
Expect(ans).To(Equal(exp))
}
var _ = Describe("Example tests", func() {
It("It should work for basic tests", func() {
dotest([] int{3,4,4,3,6,3}, []int{4,6,3})
dotest([] int{1,2,1,2,1,2,3}, []int{1,2,3})
dotest([] int{1,2,3,4}, []int{1,2,3,4})
dotest([] int{1,1,4,5,1,2,1}, []int{4,5,2,1})
dotest([] int{1,2,1,2,1,1,3}, []int{2,1,3})
dotest([] int{0,4,4,3,0,3}, []int{4,0,3})
})
})
```