golang 8. 数组 切片

数组 array.go

package main

import "fmt"

func printArray(myArray [4]int) {
	//值拷贝

	for index, value := range myArray {
		fmt.Println("index = ", index, ", value = ", value)
	}

	myArray[0] = 111
}


func main() {
	//固定长度的数组
	var myArray1 [10]int

	myArray2 := [10]int{1,2,3,4}
	myArray3 := [4]int{11,22,33,44}

	//for i := 0; i < 10; i++ {
	for i := 0; i < len(myArray1); i++ {
		fmt.Println(myArray1[i])	
	}

	for index, value := range myArray2 {
		fmt.Println("index = ", index, ", value = ", value)
	}

	//查看数组的数据类型
	fmt.Printf("myArray1 types = %T\n", myArray1)
	fmt.Printf("myArray2 types = %T\n", myArray2)
	fmt.Printf("myArray3 types = %T\n", myArray3)

	printArray(myArray3)
	fmt.Println(" ------ ")
	for index, value := range myArray3 {
		fmt.Println("index = ", index, ", value = ", value)
	}
}

切片

package main

import "fmt"

func printArray(myArray []int) {
	//引用传递
	// _ 表示匿名的变量
	for _, value := range myArray {
		fmt.Println("value = ", value)
	}

	myArray[0] = 100
}

func main() {
	myArray := []int{1,2,3,4} // 动态数组，切片 slice

	fmt.Printf("myArray type is %T\n", myArray)

	printArray(myArray)

	fmt.Println(" ==== ")

	for _, value := range myArray {
		fmt.Println("value = ", value)
	}
}

package main

import "fmt"

func main() {
	//声明slice1是一个切片，并且初始化，默认值是1，2，3。 长度len是3
	//slice1 := []int{1, 2, 3}

	//声明slice1是一个切片，但是并没有给slice分配空间
	var slice1 []int
	//slice1 = make([]int, 3) //开辟3个空间 ，默认值是0

	//声明slice1是一个切片，同时给slice分配空间，3个空间，初始化值是0
	//var slice1 []int = make([]int, 3)

	//声明slice1是一个切片，同时给slice分配空间，3个空间，初始化值是0, 通过:=推导出slice是一个切片
	//slice1 := make([]int, 3)

	fmt.Printf("len = %d, slice = %v\n", len(slice1), slice1)

	//判断一个silce是否为0
	if slice1 == nil {
		fmt.Println("slice1 是一个空切片")
	} else {
		fmt.Println("slice1 是有空间的")
	}
}

package main

import "fmt"

func main() {
	var numbers = make([]int, 3, 5)

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

	//向numbers切片追加一个元素1, numbers len = 4， [0,0,0,1], cap = 5
	numbers = append(numbers, 1)

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

	//向numbers切片追加一个元素2, numbers len = 5， [0,0,0,1,2], cap = 5
	numbers = append(numbers, 2)

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

	//向一个容量cap已经满的slice 追加元素，
	numbers = append(numbers, 3)

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

	fmt.Println("-=-------")
	var numbers2 = make([]int, 3)
	fmt.Printf("len = %d, cap = %d, slice = %v\n", len(numbers2), cap(numbers2), numbers2)
	numbers2 = append(numbers2, 1)
	fmt.Printf("len = %d, cap = %d, slice = %v\n", len(numbers2), cap(numbers2), numbers2)
	
	numbers2 = append(numbers2,2)
	numbers2 = append(numbers2,3)
	numbers2 = append(numbers2,4)
	fmt.Printf("len = %d, cap = %d, slice = %v\n", len(numbers2), cap(numbers2), numbers2)
	
	// cap * 2 
	/*
	len = 3, cap = 5, slice = [0 0 0]
	len = 4, cap = 5, slice = [0 0 0 1]
	len = 5, cap = 5, slice = [0 0 0 1 2]
	len = 6, cap = 10, slice = [0 0 0 1 2 3]
	-=-------
	len = 3, cap = 3, slice = [0 0 0]
	len = 4, cap = 6, slice = [0 0 0 1]
	len = 7, cap = 12, slice = [0 0 0 1 2 3 4]
	*/
}

package main

import "fmt"

func main() {
	s := []int{1, 2, 3} //len = 3, cap = 3, [1,2,3]

	//[0, 2)
	s1 := s[0:2] // [1, 2]

	fmt.Println(s1)

	s1[0] = 100

	fmt.Println(s)
	fmt.Println(s1)

	//copy 可以将底层数组的slice一起进行拷贝
	s2 := make([]int, 3) //s2 = [0,0,0]

	//将s中的值 依次拷贝到s2中
	copy(s2, s)
	fmt.Println(s2)

	/*
	[1 2]
	[100 2 3]
	[100 2]
	[100 2 3]
	*/
}