go语言 append函数和copy函数的应用

ゝ一世哀愁。 2022-04-03 15:50 199阅读 0赞

> **一、append函数**
> 
>  *  append函数向slice尾部追加数据，返回一个新的slice对象
> 
>     package main
>     
>     import (
>     	"fmt"
>     )
>     
>     func main() {
>     	s1 := []int{}
>     	// s1 := make(int[],0)
>     
>     	fmt.Println("s1 = ", s1)
>     	fmt.Printf("len(s1)= %d, cap(s1) = %d\n", len(s1), cap(s1))
>     
>     	s1 = append(s1, 1)
>     	s1 = append(s1, 2)
>     	s1 = append(s1, 3)
>     	fmt.Println("s1 = ", s1)                                    //s1 =  [1 2 3]
>     	fmt.Printf("len(s1)= %d, cap(s1) = %d\n", len(s1), cap(s1)) //len(s1)= 3, cap(s1) = 4
>     
>     	s2 := []int{1, 2, 3, 4}
>     	fmt.Println("s2 = ", s2)
>     	fmt.Printf("len(s2)= %d, cap(s2) = %d\n", len(s2), cap(s2))
>     	s2 = append(s2, 5)
>     	s2 = append(s2, 5)
>     	s2 = append(s2, 5)
>     	fmt.Println("s2 = ", s2)
>     	fmt.Printf("len(s2)= %d, cap(s2) = %d\n", len(s2), cap(s2)) //len(s2)= 7, cap(s2) = 8
>     }
> 
>  *  append函数会智能的进行底层数组的扩容，一旦超过了底层数组的容量，就会以2倍容量重新分配底层数组，并且拷贝原来的数据
>     
>         import "fmt"
>         
>         func main() {
>         	s := make([]int, 0, 1)
>         	c := cap(s)
>         	for i := 0; i < 70; i++ {
>         		s = append(s, i)
>         		if n := cap(s); n > c {
>         			fmt.Printf("cap:%d--->%d\n", c, n)
>         			c = n
>         		}
>         	}
>         }
>         
>         /* 结果
>         cap:1--->2
>         cap:2--->4
>         cap:4--->8
>         cap:8--->16
>         cap:16--->32
>         cap:32--->64
>         cap:64--->128
>         */
>     
>     **二、copy函数**
>     
>         package main
>         
>         import "fmt"
>         
>         func main() {
>         	srcSlice := []int{1, 2, 3}
>         	destSlice := []int{5, 5, 5, 5, 5, 5, 5}
>         	copy(destSlice, srcSlice)
>         	fmt.Println("destSlice = ", destSlice) //destSlice =  [1 2 3 5 5 5 5]
>         }
>     
>