在Go中,字符串是一种基本类型,这意味着它是只读的,对它的每次操作都会创建一个新字符串。
如果我想多次连接字符串而不知道结果字符串的长度,最好的方法是什么?
最天真的做法是:
var s string
for i := 0; i < 1000; i++ {
s += getShortStringFromSomewhere()
}
return s
但这似乎不是很有效。
在Go中,字符串是一种基本类型,这意味着它是只读的,对它的每次操作都会创建一个新字符串。
如果我想多次连接字符串而不知道结果字符串的长度,最好的方法是什么?
最天真的做法是:
var s string
for i := 0; i < 1000; i++ {
s += getShortStringFromSomewhere()
}
return s
但这似乎不是很有效。
当前回答
简单易消化的解决方案。详情请见评论。 Copy覆盖slice的元素。我们对单个元素进行切片,然后覆盖它。
package main
import (
"fmt"
)
var N int = 100000
func main() {
slice1 := make([]rune, N, N)
//Efficient with fast performance, Need pre-allocated memory
//We can add a check if we reached the limit then increase capacity
//using append, but would be fined for data copying to new array. Also append happens after the length of current slice.
for i := 0; i < N; i++ {
copy(slice1[i:i+1], []rune{'N'})
}
fmt.Println(slice1)
//Simple but fast solution, Every time the slice capacity is reached we get a fine of effort that goes
//in copying data to new array
slice2 := []rune{}
for i := 0; i <= N; i++ {
slice2 = append(slice2, 'N')
}
fmt.Println(slice2)
}
其他回答
我只是在我自己的代码(递归树遍历)中对上面发布的顶部答案进行了基准测试,简单的concat操作符实际上比BufferString更快。
func (r *record) String() string {
buffer := bytes.NewBufferString("");
fmt.Fprint(buffer,"(",r.name,"[")
for i := 0; i < len(r.subs); i++ {
fmt.Fprint(buffer,"\t",r.subs[i])
}
fmt.Fprint(buffer,"]",r.size,")\n")
return buffer.String()
}
这花了0.81秒,而下面的代码:
func (r *record) String() string {
s := "(\"" + r.name + "\" ["
for i := 0; i < len(r.subs); i++ {
s += r.subs[i].String()
}
s += "] " + strconv.FormatInt(r.size,10) + ")\n"
return s
}
只花了0.61秒。这可能是由于创建新BufferString的开销。
更新:我还对连接函数进行了基准测试,它在0.54秒内运行。
func (r *record) String() string {
var parts []string
parts = append(parts, "(\"", r.name, "\" [" )
for i := 0; i < len(r.subs); i++ {
parts = append(parts, r.subs[i].String())
}
parts = append(parts, strconv.FormatInt(r.size,10), ")\n")
return strings.Join(parts,"")
}
使用内存分配统计信息的基准测试结果。在github检查基准代码。
使用字符串。构建器来优化性能。
go test -bench . -benchmem
goos: darwin
goarch: amd64
pkg: github.com/hechen0/goexp/exps
BenchmarkConcat-8 1000000 60213 ns/op 503992 B/op 1 allocs/op
BenchmarkBuffer-8 100000000 11.3 ns/op 2 B/op 0 allocs/op
BenchmarkCopy-8 300000000 4.76 ns/op 0 B/op 0 allocs/op
BenchmarkStringBuilder-8 1000000000 4.14 ns/op 6 B/op 0 allocs/op
PASS
ok github.com/hechen0/goexp/exps 70.071s
简单易消化的解决方案。详情请见评论。 Copy覆盖slice的元素。我们对单个元素进行切片,然后覆盖它。
package main
import (
"fmt"
)
var N int = 100000
func main() {
slice1 := make([]rune, N, N)
//Efficient with fast performance, Need pre-allocated memory
//We can add a check if we reached the limit then increase capacity
//using append, but would be fined for data copying to new array. Also append happens after the length of current slice.
for i := 0; i < N; i++ {
copy(slice1[i:i+1], []rune{'N'})
}
fmt.Println(slice1)
//Simple but fast solution, Every time the slice capacity is reached we get a fine of effort that goes
//in copying data to new array
slice2 := []rune{}
for i := 0; i <= N; i++ {
slice2 = append(slice2, 'N')
}
fmt.Println(slice2)
}
如果你有一个字符串切片,你想要有效地转换成一个字符串,那么你可以使用这种方法。否则,看看其他答案。
在strings包中有一个名为Join的库函数: http://golang.org/pkg/strings/#Join
看看Join的代码,可以看到Kinopiko写的类似于Append函数的方法:https://golang.org/src/strings/strings.go#L420
用法:
import (
"fmt";
"strings";
)
func main() {
s := []string{"this", "is", "a", "joined", "string\n"};
fmt.Printf(strings.Join(s, " "));
}
$ ./test.bin
this is a joined string
我使用以下方法:-
package main
import (
"fmt"
"strings"
)
func main (){
concatenation:= strings.Join([]string{"a","b","c"},"") //where second parameter is a separator.
fmt.Println(concatenation) //abc
}