go语言渐入佳境[13]-切片

//切片的声明1  //nil
var slice1 []int  

//切片的声明2
var slice2 []int = make([]int,5)
var slice3 []int = make([]int,5,7)
numbers:= []int{1,2,3,4,5,6,7,8}

numbers:= []int{1,2,3,4,5,6,7,8}
//从下标1一直到下标4，但是不包括下标4
numbers1 :=numbers[1:4]
//从下标0一直到下标3，但是不包括下标3
numbers2 :=numbers[:3]
//从下标3一直到结束
numbers3 :=numbers[3:]

package main

import "fmt"

//1、切片可以修改大小

//2、切片的拷贝不是单纯值的拷贝，一个切片指向了一个数组


//切片的声明1
var slice1 []int

//切片的声明2
var slice2 []int = make([]int,5)
var slice3 []int = make([]int,5,7)

func main(){


	slice4 := make([]int,5)
	slice5 := make([]int,5,7)

	slice6 := make([]int,0)


	fmt.Printf("len=%d,cap=%d,slice=%v\n",len(slice4),cap(slice4),slice4)
	fmt.Printf("len=%d,cap=%d,slice=%v",len(slice5),cap(slice5),slice5)


	if slice4 ==nil{
		fmt.Printf("len=%d,cap=%d,slice=%v\n",len(slice4),cap(slice4),slice4)

	}
	//	slice6 := make([]int,0)不为nil
	if slice6 !=nil{
		fmt.Printf("len=%d,cap=%d,slice=%v\n",len(slice6),cap(slice6),slice6)

	}
	//var slice1 []int为nil
	if slice1 ==nil{
		fmt.Printf("len=%d,cap=%d,slice=%v\n",len(slice1),cap(slice1),slice1)

	}

	sliceTest()
}

//截取
func sliceTest(){
	numbers:= []int{1,2,3,4,5,6,7,8}
	printSliceInfo(numbers)

	numbers1 :=numbers[1:4]
	printSliceInfo(numbers1)


	numbers2 :=numbers[:3]
	printSliceInfo(numbers2)

	numbers3 :=numbers[3:]
	printSliceInfo(numbers3)
}
//打印切片
func printSliceInfo(x []int){

	fmt.Printf("len=%d,cap=%d,slice=%v\n",len(x),cap(x),x)
}

//	切片删除
//	删除第一个元素
numbers = numbers[1:]   

//	删除最后一个
numbers = numbers[:len(numbers)-1]

//删除中间一个元素
a := int(len(numbers) / 2)
numbers = append(numbers[:a], numbers[a+1:]...)

package main

import "fmt"

func main() {
	//数组是值类型
	a := [4]int{1, 2, 3, 4}

	//切片是引用类型
	b := []int{100, 200, 300}

	c := a
	d := b

	c[1] = 200
	d[0] = 1

	fmt.Println("a=", a, "c=", c)
	//c[1 200 3 4] a[1 2 3 4]
	fmt.Println("b=", b, "d=", d)
	//d[1 200 300]  b[1 200 300]
}

numbers := make([]int, 0, 20)


//append一个元素
numbers = append(numbers, 0)

//append多个元素
numbers = append(numbers, 1, 2, 3, 4, 5, 6, 7)


//append添加切片
s1 := []int{100, 200, 300, 400, 500, 600, 700}
numbers = append(numbers, s1...) //[0 1 2 3 4 5 6 7 100 200 300 400 500 600 700]

//创建目标切片
numbers1 := make([]int, len(numbers), cap(numbers)*2)

//	将numbers的元素拷贝到numbers1中
count := copy(numbers1, numbers)

package main

import "fmt"

func main() {
	fmt.Println("1、--------------")
	//var numbers []int
	numbers := make([]int, 0, 20)


	//append一个元素
	numbers = append(numbers, 0)
	printSlice("numbers:", numbers) //[0]

	//append多个元素
	numbers = append(numbers, 1, 2, 3, 4, 5, 6, 7)
	printSlice("numbers:", numbers) //[0 1 2 3 4 5 6 7]

	//append添加切片
	s1 := []int{100, 200, 300, 400, 500, 600, 700}
	numbers = append(numbers, s1...) //[0 1 2 3 4 5 6 7 100 200 300 400 500 600 700]
	printSlice("numbers:", numbers)





	fmt.Println("2、--------------")
	//	切片删除
	//	删除第一个元素
	numbers = numbers[1:]
	printSlice("numbers:", numbers) //[ 1 2 3 4 5 6 7 100 200 300 400 500 600 700]

	//	删除最后一个
	numbers = numbers[:len(numbers)-1]
	printSlice("numbers:", numbers) //[ 1 2 3 4 5 6 7 100 200 300 400 500 600]

	//删除中间一个元素
	a := int(len(numbers) / 2)
	fmt.Println("中间下标：", a)
	numbers = append(numbers[:a], numbers[a+1:]...)
	printSlice("numbers:", numbers) //[1 2 3 4 5 6 100 200 300 400 500 600]




	fmt.Println("3、--------------")
	//创建目标切片
	numbers1 := make([]int, len(numbers), cap(numbers)*2)

	//	将numbers的元素拷贝到numbers1中
	count := copy(numbers1, numbers)
	fmt.Println("拷贝的个数：", count)
	printSlice("numbers1:", numbers1)

	//拷贝的两个切片是否有关联
	numbers[0] = 99
	numbers1[len(numbers1)-1] = 100

	printSlice("numbers", numbers)
	printSlice("numbers1", numbers1)

}

func printSlice(name string, x []int) {
	fmt.Print(name, "\t")
	fmt.Printf("地址：%p \t len=%d \t cap=%d \t value=%v \n", x, len(x), cap(x), x)
}

package main

import "fmt"

func f(s []string, level int) {
        if level > 5 {
               return
        }
        s = append(s, fmt.Sprint(level))
        f(s, level+1)
        fmt.Println("level:", level, "slice:", s)
}

func main() {
        f(nil, 0)
}

level: 5 slice: [0 1 2 3 4 5]
level: 4 slice: [0 1 2 3 4]
level: 3 slice: [0 1 2 3]
level: 2 slice: [0 1 2]
level: 1 slice: [0 1]
level: 0 slice: [0]