Swift学习笔记(5)--数组

数组的下标从0开始计数,相关方法属性涉及到下标时也从0开始计数

1.定义:

//1.可变数组
var cityArray = ["Portland","San Francisco","Cupertino"]
//2.不可变数组
let cityArray2 = ["Portland","San Francisco","Beijing"]
//3.空数组
var animalArray = String[]()
var animalAgeArray = Int[]()

　　

2.基本方法:统计总数,判断非空

//1.统计总数
var cityArray: String[] = ["Portland","San Francisco","Cupertino"]
let count = cityArray.count

//2.判断非空
if cityArray.isEmpty {
    println("Empty")
}else{
    println("Not Empty")
}

　　

3.遍历

var animalArray: String[] = ["Dog", "Cat", "Fish", "Owl" ]

//1.元素遍历
for animal in animalArray {
    println(animal)
}

//2.带下标遍历
for(index,animal) in enumerate(animalArray) {

    println("The \(animal) is at index:\(index)")

}

for var i = 0; i < animalArray.count; i++ {
    println(animalArray[i])
}

for i in 0..animalArray.count {
    println(animalArray[i])
}

　　

4.添加元素或者子数组

//1.添加单个元素
var cityArray: String[] = ["Portland","San Francisco","Cupertino"]
cityArray.append("Seattle") //函数添加
cityArray += "Seattle"      //运算符重载添加

//2.添加子数组
var cityArrayA: String[] = ["Portland","San Francisco","Cupertino","Seattle"]
var cityArrayB: String[] = ["Vancouver", "Los Angeles", "Eugene"]

cityArrayA += ["Vancouver", "Los Angeles", "Eugene"]  //固定子数组
cityArrayA += cityArrayB;   //变量子数组

　　

5.改变数组元素

　　注:改变多个元素,如果下标与元素的数量不一致,以下标做多退少补

var cityArray: String[] = ["Portland","San Francisco","Cupertino","Seattle","NewYork"]

//1.改变单个元素
cityArray[0] = "Oregon"

//2.改变多个元素,如果下标与元素的数量不一致,以下标做多退少补
    //2.1 相等时
var cityArray0 = cityArray
cityArray0[0...2] = ["Beijing","Shanghai","Guangzhou"]
println(cityArray0) //[Beijing, Shanghai, Guangzhou, Seattle, NewYork]
    //2.2 下标多于元素时,原数组中多出的下标数据被remove出原数组,即多退
var cityArray2 = cityArray
cityArray2[0...3] = ["Beijing","Shanghai","Guangzhou"]
println(cityArray2) //[Beijing, Shanghai, Guangzhou, NewYork]
    //2.3 下标少于元素时,将多出的元素添加到原数组,即少补
var cityArray3 = cityArray
cityArray3[0...1] = ["Beijing","Shanghai","Guangzhou"]
println(cityArray3) //[Beijing, Shanghai, Guangzhou, Cupertino, Seattle, NewYork]

　　

6.删除元素

//1.删除指定元素
var animalArray: String[] = ["Dog", "Cat", "Fish", "Owl", "Beaver"]
animalArray.removeAtIndex(4)
println(animalArray)    //[Dog, Cat, Fish, Owl]

//2.删除最后一个元素
var animalArray2: String[] = ["Dog", "Cat", "Fish", "Owl" ]
animalArray2.removeLast()   //[Dog, Cat, Fish]
println(animalArray2)

//3.删除所有元素
var animalArray3: String[] = ["Dog", "Cat", "Fish", "Owl" ]
animalArray3.removeAll()
println(animalArray3)   //[]

　　

注：如果你想保留原来被删除的元素,可以使用let item = array.removeFunction() 来保留　　

var animalArray: String[] = ["Dog", "Cat", "Fish", "Owl", "Beaver"]
let item = animalArray.removeAtIndex(4)
println(item)    //Beaver

　　

7.排序

基本排序

var animalArray: String[] = ["Dog", "Cat", "Fish", "Owl" ]
sort(animalArray)
//The array values are now [Cat, Dog, Fish, Owl]

　　

反向重排

var animalArray: String[] = ["Dog", "Cat", "Fish", "Owl" ]
animalArray.reverse()
//The array values are now ["Owl", "Fish", "Cat", "Dog"]

　　

自定义快速排序

func quicksort_swift(inout a:Int[], start:Int, end:Int) {
    if (end - start < 2){
        return
    }
    var p = a[start + (end - start)/2]
    var l = start
    var r = end - 1
    while (l <= r){
        if (a[l] < p){
            l += 1
            continue
        }
        if (a[r] > p){
            r -= 1
            continue
        }
        var t = a[l]
        a[l] = a[r]
        a[r] = t
        l += 1
        r -= 1
    }
    quicksort_swift(&a, start, r + 1)
    quicksort_swift(&a, r + 1, end)
}

var a_swift:Int[] = [0,5,2,8,1234,-1,2]
let swift_start:UInt64 = mach_absolute_time();
println(swift_start)
quicksort_swift(&a_swift, 0, a_swift.count)
let swift_stop:UInt64 = mach_absolute_time();
println(swift_stop)
println(a_swift)