var arr1 = [1,3,4,6,7]

var arr2 = [1,2,3,4,5,6,7,8,9]

var result = [Int]()

var index = 0

for a1 in arr1{
    for a2 in arr2{
       if a1 != a2{
            //如果不重复就两个都要
            result[index] = a1
            index++
            result[index] = a2
            index++
       }else{
            //重复只要一个
            result[index] = a1
            index++
        }  
    }
}

for val in result{
   print(val)
}