Split string by length in Golang

问题

Does anyone know how to split a string in Golang by length?

For example to split "helloworld" after every 3 characters, so it should ideally return an array of "hel" "low" "orl" "d"?

Alternatively a possible solution would be to also append a newline after every 3 characters..

All ideas are greatly appreciated!

回答1:

Make sure to convert your string into a slice of rune: see "Slice string into letters".

for automatically converts string to rune so there is no additional code needed in this case to convert the string to rune first.

for i, r := range s {
    fmt.Printf("i%d r %c\n", i, r)
    // every 3 i, do something
}

r[n:n+3] will work best with a being a slice of rune.

The index will increase by one every rune, while it might increase by more than one for every byte in a slice of string: "世界": i would be 0 and 3: a character (rune) can be formed of multiple bytes.

For instance, consider s := "世a界世bcd界efg世": 12 runes. (see play.golang.org)

If you try to parse it byte by byte, you will miss (in a naive split every 3 chars implementation) some of the "index modulo 3" (equals to 2, 5, 8 and 11), because the index will increase past those values:

for i, r := range s {
    res = res + string(r)
    fmt.Printf("i %d r %c\n", i, r)
    if i > 0 && (i+1)%3 == 0 {
        fmt.Printf("=>(%d) '%v'\n", i, res)
        res = ""
    }
}

The output:

i  0 r 世
i  3 r a   <== miss i==2
i  4 r 界
i  7 r 世  <== miss i==5
i 10 r b  <== miss i==8
i 11 r c  ===============> would print '世a界世bc', not exactly '3 chars'!
i 12 r d
i 13 r 界
i 16 r e  <== miss i==14
i 17 r f  ===============> would print 'd界ef'
i 18 r g
i 19 r 世 <== miss the rest of the string

But if you were to iterate on runes (a := []rune(s)), you would get what you expect, as the index would increase one rune at a time, making it easy to aggregate exactly 3 characters:

for i, r := range a {
    res = res + string(r)
    fmt.Printf("i%d r %c\n", i, r)
    if i > 0 && (i+1)%3 == 0 {
        fmt.Printf("=>(%d) '%v'\n", i, res)
        res = ""
    }
}

Output:

i 0 r 世
i 1 r a
i 2 r 界 ===============> would print '世a界'
i 3 r 世
i 4 r b
i 5 r c ===============> would print '世bc'
i 6 r d
i 7 r 界
i 8 r e ===============> would print 'd界e'
i 9 r f
i10 r g
i11 r 世 ===============> would print 'fg世'

回答2:

Also needed a function to do this recently, see example usage here

func SplitSubN(s string, n int) []string {
    sub := ""
    subs := []string{}

    runes := bytes.Runes([]byte(s))
    l := len(runes)
    for i, r := range runes {
        sub = sub + string(r)
        if (i + 1) % n == 0 {
            subs = append(subs, sub)
            sub = ""
        } else if (i + 1) == l {
            subs = append(subs, sub)
        }
    }

    return subs
}

回答3:

Here is another example (you can try it here):

package main

import (
    "fmt"
    "strings"
)

func ChunkString(s string, chunkSize int) []string {
    var chunks []string
    runes := []rune(s)

    if len(runes) == 0 {
        return []string{s}
    }

    for i := 0; i < len(runes); i += chunkSize {
        nn := i + chunkSize
        if nn > len(runes) {
            nn = len(runes)
        }
        chunks = append(chunks, string(runes[i:nn]))
    }
    return chunks
}

func main() {
    fmt.Println(ChunkString("helloworld", 3))
    fmt.Println(strings.Join(ChunkString("helloworld", 3), "\n"))
}

回答4:

I tried 3 version to implement the function, the function named "splitByWidthMake" is fastest.

These functions ignore the unicode but only the ascii code.

package main

import (
    "fmt"
    "strings"
    "time"
    "math"
)

func splitByWidthMake(str string, size int) []string {
    strLength := len(str)
    splitedLength := int(math.Ceil(float64(strLength) / float64(size)))
    splited := make([]string, splitedLength)
    var start, stop int
    for i := 0; i < splitedLength; i += 1 {
        start = i * size
        stop = start + size
        if stop > strLength {
            stop = strLength
        }
        splited[i] = str[start : stop]
    }
    return splited
}



func splitByWidth(str string, size int) []string {
    strLength := len(str)
    var splited []string
    var stop int
    for i := 0; i < strLength; i += size {
        stop = i + size
        if stop > strLength {
            stop = strLength
        }
        splited = append(splited, str[i:stop])
    }
    return splited
}

func splitRecursive(str string, size int) []string {
    if len(str) <= size {
        return []string{str}
    }
    return append([]string{string(str[0:size])}, splitRecursive(str[size:], size)...)
}

func main() {
    /*
    testStrings := []string{
        "hello world",
        "",
        "1",
    }
    */

    testStrings := make([]string, 10)
    for i := range testStrings {
        testStrings[i] = strings.Repeat("#", int(math.Pow(2, float64(i))))
    }

    //fmt.Println(testStrings)

    t1 := time.Now()
    for i := range testStrings {
        _ = splitByWidthMake(testStrings[i], 2)
        //fmt.Println(t)
    }
    elapsed := time.Since(t1)
    fmt.Println("for loop version elapsed: ", elapsed)


    t1 = time.Now()
    for i := range testStrings {
        _ = splitByWidth(testStrings[i], 2)
    }
    elapsed = time.Since(t1)
    fmt.Println("for loop without make version elapsed: ", elapsed)




    t1 = time.Now()
    for i := range testStrings {
        _ = splitRecursive(testStrings[i], 2)
    }
    elapsed = time.Since(t1)
    fmt.Println("recursive version elapsed: ", elapsed)

}

回答5:

An easy solution using regex

re := regexp.MustCompile((\S{3})) x := re.FindAllStringSubmatch("HelloWorld", -1) fmt.Println(x)

https://play.golang.org/p/mfmaQlSRkHe

来源：https://stackoverflow.com/questions/25686109/split-string-by-length-in-golang

标签

string

split

string-length