func getConcatenation(nums []int) []int { ans := make([]int, 2*len(nums)) for i, n := range nums { ans[i] = n ans[len(nums)+i] = n } return ans } main.go
func getConcatenation(nums []int) []int { ans := make([]int, 2*len(nums)) for i, n := range nums { ans[i] = n ans[len(nums)+i] = n } return ans }