swift array 操作

1. filter
   //filter用于选择数组元素中满足某种条件的元素。

var arr = [1,3,4,5,7,5];
var filteredArray = arr.filter({$0 > 4})
var tt = arr.filter { (num) -> Bool in
num > 4
}
print(filteredArray) //[5, 7, 5]
print(tt) //[5, 7, 5]