dtg25862
dtg25862
2019-06-13 04:47
浏览 210
已采纳

如何将一个切片的内容复制到另一个切片中

I'm doing below exercise in go.

Create a slice with four elements. Create a new slice and copy the third and fourth elements only into it.

I have return the below program

    package main

    import "fmt"

    func main() {
        var elements = make([]string, 4)
        elements[0] = "1"
        elements[1] = "2"
        elements[2] = "3"
        elements[3] = "4"
        fmt.Println(elements)

        var newElements = make([]string, 2)
        newElements = append(elements[:0], elements[:2]...)
        fmt.Println(newElements)
    }

output of my program is. But I want the newElements slice to be [3 4]-

[1 2 3 4]
[1 2]

What is wrong in my program.

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2条回答 默认 最新

  • duanpo2813
    duanpo2813 2019-06-13 04:52
    已采纳

    Use the built-in copy function to copy elements from one slice to another.

    var newElements = make([]string, 2)
    copy(newElements, elements[2:])
    

    Run it on the playground

    You can use append to create the slice and copy the elements in a single statement, but the code is not as obvious as using copy.

    newElements := append([]string(nil), elements[2:4]...)
    

    Run it on the playground.

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  • dsvjw20866
    dsvjw20866 2019-06-13 04:52

    Problem is in the line newElements = append(elements[:0], elements[:2]...). Here elements[:2] means elements elements[0], elements[1]. That's why your output is [1,2]. For third and fourth elements use this elements[2:4].

    package main
    
    import "fmt"
    
    func main() {
        var elements = make([]string, 4)
        elements[0] = "1"
        elements[1] = "2"
        elements[2] = "3"
        elements[3] = "4"
        fmt.Println(elements)
    
        var newElements = make([]string, 2)
        newElements = append(elements[:0], elements[2:4]...)
        fmt.Println(newElements)
    }
    
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