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# 一、数组
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和java、python数组类似，使用[]来表示
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```
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var identifier [len]type
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```
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表示声明一个长度为5的数组,下标从0开始且长度不可变
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```go
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var a [5]int
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```
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表示声明一个数组，并初始化4个值，与 var a =[4]string{"a", "b", "c", "d"} 相同，用于数组常量
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```go
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a := [...]string{"a", "b", "c", "d"}
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```
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数组常量
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```go
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//初始10位数组，除前3位外都是0
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var arrAge = [10]int{18, 20, 15}
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var arrLazy = [...]int{5, 6, 7, 8, 22}
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var arrLazy = []int{5, 6, 7, 8, 22}
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//根据下标指定值
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var arrKeyValue = []string{3: "Chris", 4: "Ron"}
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```
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## 1.1 数组遍历
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第一种：
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```go
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func main() {
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var a [10]int
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for i := 0; i < len(a); i++ {
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a[i] = i * 2
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}
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//遍历
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for i := 0; i < len(a); i++ {
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println(a[i])
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}
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}
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```
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第二种：
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```go
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func main() {
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var a [10]int
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for i := 0; i < len(a); i++ {
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a[i] = i * 2
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}
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//for-range遍历,第一个返回值 ix 是数组或者切片的索引，第二个是在该索引位置的值；value 只是 slice1 某个索引位置的值的一个拷贝，不能用来修改 slice1 该索引位置的值。
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for ix,value := range a {
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println(a[ix])
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}
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//也可以只要索引
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for ix := range a {
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println(a[ix])
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}
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}
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```
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# 二、切片
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切片可以理解为动态数组，是**引用类型**,与数组相比切片的长度是不固定的，可以追加元素，在追加时可能使切片的容量增大。可以理解为java中的list
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声明一个切片的格式，不需要写长度
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```go
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var identifier []type
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```
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数组转切片，有点类似python
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```go
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var slice1 []type = arr1[start:end]
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```
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## 2.1 切片初始化
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```go
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var slice1 []type = make([]type, len)
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//也可以简写为
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slice1 := make([]type, len)
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//也可以指定容量，其中capacity为可选参数
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make([]T, length, capacity)
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```
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```go
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////直接初始化切片，[]表示是切片类型，{1,2,3}初始化值依次是1,2,3.其cap=len=3
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s :=[] int {1,2,3 }
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//初始化切片s,是数组arr的引用
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s := arr[:]
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//将arr中从下标startIndex到endIndex-1 下的元素创建为一个新的切片
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s := arr[startIndex:endIndex]
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//缺省endIndex时将表示一直到arr的最后一个元素
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s := arr[startIndex:]
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//缺省startIndex时将表示从arr的第一个元素开始
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s := arr[:endIndex]
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//通过切片s初始化切片s1
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s1 := s[startIndex:endIndex]
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//通过内置函数make()初始化切片s,[]int 标识为其元素类型为int的切片
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s :=make([]int,len,cap)
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```
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## 2.2 切片截取
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与python方式相同
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```go
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s :=[] int {1,2,3 }
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//表示从第1个元素开始截取，结果为2、3
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s1:=s[1:]
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```
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```go
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s := []int{1, 2, 3, 4, 5, 6, 7}
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//表示从第1个元素开始截取,不包含第3个元素，结果为2、3
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s1 := s[1:3]
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```
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## 2.3 append()和copy()
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向切片追加元素
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```go
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var numbers []int
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printSlice(numbers)
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/* 允许追加空切片 */
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numbers = append(numbers, 0)
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printSlice(numbers)
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/* 向切片添加一个元素 */
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numbers = append(numbers, 1)
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printSlice(numbers)
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/* 同时添加多个元素 */
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numbers = append(numbers, 2,3,4)
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printSlice(numbers)
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/* 创建切片 numbers1 是之前切片的两倍容量*/
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numbers1 := make([]int, len(numbers), (cap(numbers))*2)
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/* 拷贝 numbers 的内容到 numbers1 */
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copy(numbers1,numbers)
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printSlice(numbers1)
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```
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## 2.4 copy()
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复制切片
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