Swift查找第一个只出现一次的字符

extension ViewController {
    func getFirstChar(_ str: String) -> String {
        var dic: Dictionary<String, Int> = [:]
        
        for i in str {
            if let val = dic[String(i)] {
                dic.updateValue(val + 1, forKey: String(i))
            } else {
                dic.updateValue(1, forKey: String(i))
            }
        }
        
        for i in str {
            if dic[String(i)] == 1 {
                return String(i)
            }
        }
        
        return ""
    }
}

var str = "sabsabcd"
        var s = getFirstChar(str)
        print(s)

打印结果

c