如何检查Go中的字符串切片是否包含某个值？

Question

检查某个值是否在字符串片中的最佳方法是什么？我会用其他语言的集合，但是Go没有。到目前为止，我最大的努力是：.

package main

import "fmt"

func main() {
    list := []string{"a", "b", "x"}
    fmt.Println(isValueInList("b", list))
    fmt.Println(isValueInList("z", list))
}

func isValueInList(value string, list []string) bool {
    for _, v := range list {
        if v == value {
            return true
        }
    }
    return false
}

http://play.golang.org/p/gkwMz5j09n

这个解决方案对于小片应该是可以的，但是对于有许多元素的片应该怎么做呢？

Answer 1

If you have a slice of strings in an arbitrary order, finding if a value exists in the slice requires O(n) time. This applies to all languages.

If you intend to do a search over and over again, you can use other data structures to make lookups faster. However, building these structures require at least O(n) time. So you will only get benefits if you do lookups using the data structure more than once.

For example, you could load your strings into a map. Then lookups would take O(1) time. Insertions also take O(1) time making the initial build take O(n) time:

set := make(map[string]bool)
for _, v := range list {
    set[v] = true
}

fmt.Println(set["b"])

You can also sort your string slice and then do a binary search. Binary searches occur in O(log(n)) time. Building can take O(n*log(n)) time.

sort.Strings(list)
i := sort.SearchStrings(list, "b")
fmt.Println(i < len(list) && list[i] == "b")

Although in theory given an infinite number of values, a map is faster, in practice it is very likely searching a sorted list will be faster. You need to benchmark it yourself.