快速过滤数组元素

Question

I am creating a function that will filter an array,
eg x = [10,20,30,40,50]
filter(x,10,20)
output should be 30,40,50.
I am getting an index out of bounds error . Here's my code:

func filterArray( _ x:  [Int], _ nums: Int...) -> [Int]{
var arrayX = x
    for i in 0...arrayX.count-1{
        for j in 0...nums.count-1 {
            if arrayX[i] == nums[j]{//Changed arrayX to x because x was never changed
             if let index = arrayX.index(of: nums[j]) {
                    arrayX.remove(at: index) //error is here
                }
                else{

                }
            }
        }
    }
    return arrayX
}

var mArray = [10,20,30,40,50]
filterArray(mArray,10)

Answer 1

The way you are doing it is not correct, you are altering an array while looping through it. When you remove an object from the array, the array count changes but the loop still run using the previously calculated array.count value.

There is a much simpler way of doing this, you just need to combine filter and contains functions together for achieving this:

func filterArray( _ x:  [Int], _ nums: Int...) -> [Int]
{
    let filteredArray = x.filter({ !nums.contains($0)})
    return filteredArray
}

Answer 2

从数组中删除一个元素后，其大小会发生变化，但是循环仍将继续进行，直到导致该问题的先前计数为止，尝试使其他数组通过该循环并存储结果，而无需找到其索引已经存在，“ i”的值就是元素的索引。

Answer 3

You function can be faster if you use a Set .

func filter(list: [Int], _ remove: Int...) -> [Int] {
    let removeSet = Set(remove)
    return list.filter { removeSet.contains($0) }
}