数组中取最大值最小值方法

• 排序

let list = [2.3,3,6,1,-11,55,66,33,21,5,77,33]
list.sorted()
list.sorted { (a, b) -> Bool in
    return a

• KVC

let arr:NSArray = ["a","d","f","k","g"]
arr.value(forKeyPath: "@max.self")//k
arr.value(forKeyPath: "@min.self")//a

• swift新方法

let arr = ["a","d","f","k","g"]
arr.max()//k
arr.min()//a