go语言切片 slice(深浅拷贝删除)

切片与map类似是引用 需要make进行初始化
make([]int,size,cap)
make 指定slice的长度以及容量

func SliceTest5() {
	s1 := make([]int,10,20)
	fmt.Println(s1)
}

切片赋值 99为索引，给索引为99的slice赋值

func SliceTest5() {
	s1 := []int{99: 1, 1, 2}
	fmt.Println(s1)
}

func main() {
	SliceTest5()
}

go slice相当于是数组的引用，slice赋值属于浅拷贝如下：

func SliceTest2() {
	s1 := []int{1, 2, 3, 4}
	s2 := s1
	s2[1] = 10
	fmt.Printf("s2 contenxt is %+v len is %d,cap is %d\n", s2, len(s2), cap(s2))
	fmt.Printf("s1 contenxt is %+v len is %d,cap is %d\n", s1, len(s1), cap(s1))
}

s2 contenxt is [1 10 3 4] len is 4,cap is 4
s1 contenxt is [1 10 3 4] len is 4,cap is 4
s1 s2的第二个元素都变了

如何深拷贝

func SliceTest3() {
	s1 := []int{1, 2, 3, 4}
	s2 := make([]int, 4, 10)
	copy(s2, s1)
	s2[1] = 10
	fmt.Printf("s2 contenxt is %+v len is %d,cap is %d\n", s2, len(s2), cap(s2))
	fmt.Printf("s1 contenxt is %+v len is %d,cap is %d\n", s1, len(s1), cap(s1))
}

只有s2变了
C:\goProject\src\day02>day02.exe
s2 contenxt is [1 10 3 4] len is 4,cap is 10
s1 contenxt is [1 2 3 4] len is 4,cap is 4

切片的首尾范围
0<=lower<=higher<=len(slice)
三个元素lower higher max
slice[lower:higher:max]
0<=lower<=higher<=max
cap为max-lower
对于切片的切片

func SliceTest1() {
	s1 := []int{1, 2, 3, 4}
	s2 := s1[1:2:3]
	fmt.Printf("s2 contenxt is %+v len is %d,cap is %d", s2, len(s2), cap(s2))
}

打印结果
C:\goProject\src\day02>day02.exe
s2 contenxt is [2] len is 1,cap is 2

切片元素删除

func SliceTest4() {
	s1 := []int{1, 2, 3, 4}
	s2 := s1
	s1 = append(s1[:1], s1[2:]...)
	fmt.Printf("s1 contenxt is %+v len is %d,cap is %d\n", s1, len(s1), cap(s1))
	fmt.Printf("s2 contenxt is %+v len is %d,cap is %d\n", s2, len(s2), cap(s2))
}

func main() {
	SliceTest4()
}

C:\goProject\src\day02>day02.exe
s2 contenxt is [1 3 4] len is 3,cap is 4
s2 contenxt is [1 3 4 4] len is 4,cap is 4

append数组追加元素必须要有返回值

func SliceTest4() {
	s1 := []int{1, 2, 3, 4}
	s2 := make([]int, 4, 10)
	fmt.Printf("s1 contenxt is %+v len is %d,cap is %d\n", s1, len(s1), cap(s1))
	s1 = append(s1[:1], s2...) //必须有三个点
	fmt.Printf("s1 contenxt is %+v len is %d,cap is %d\n", s1, len(s1), cap(s1))
	 
}

由于s1原来只有size 4 cap 4，但是后面追加了4ge元素扩容了为8
s1 contenxt is [1 2 3 4] len is 4,cap is 4
s1 contenxt is [1 0 0 0 0] len is 5,cap is 8