sol2.go

sol2.go

func sol2(arr []int) int {
	mapCheck := make(map[int]int)

	for i := 0; i < len(arr); i++ {
		mapCheck[arr[i]]++
	}

	for key, value := range mapCheck {
		if value > 1 {
			return key
		}
	}

	return -1
}