/** 判断字符出现的次数 */
        let str = "asfkj294sjdkflskadjw8tghjhf8t8as"
        //定义一个字典统计个字符的出现次数
        var status : [Character : Int] = [:]
        for ch in str
        {
            //获取ch字符出现的次数
            var num = status[ch]
            //如果一次未出现，会返回nil
            if num != nil
            {
                status[ch] = num! + 1
            }
            else
            {
                status[ch] = 1
            }

        }
        //[j: 4,w: 1,f: 3,9: 1,k: 3,d: 2,t: 2,2: 1,a: 3,8: 3,4: 1,s: 4,l: 1,g: 1,h: 2]
        println(status)

        //遍历status的value集合，找出最大的出现次数
        var maxOccurs = 0
        for occurs in Array(status.values)
        {
            if occurs > maxOccurs
            {
                maxOccurs = occurs
            }
        }
        //找出最后出现次数最多的对应字符
        for (ch,occurs) in status
        {
            if occurs == maxOccurs
            {
                //出现最多的字符 j,出现的次数4
                //出现最多的字符 s,出现的次数4
                println("出现最多的字符 \(ch),出现的次数\(occurs)")
            }
        }