67. The algorithm is simple and swift look different

Given two strings s and t, which contain only lowercase letters.

String rearrangement t s by the random string, and add a letter at random locations.

Find the letters are added in t.

 

Example:

输入：
s = "abcd"
t = "abcde"

Output:
E

Interpretation:
'E' that is being added letters.

solution:

    func findTheDifference(_ s: String, _ t: String) -> Character {
         var s = s
        
        for item in t {
            if let index = s.firstIndex(of: item) {
                s.remove(at: index)
                
            }else{
                return item
            }
        }
        return Character("")
    }