如果无法使用Go lang对地图进行排序，那么正确的方法是什么？

问题描述：

Let's say I have a string and I would like to count each letter's frequency and then sort the table by the frequency. Desired output of "hello larry" would be:

+--------+-----------+
| Letter | Occurence |
+--------+-----------+
| l      |         3 |
| r      |         2 |
| h      |         1 |
| e      |         1 |
| o      |         1 |
| a      |         1 |
| y      |         1 |
+--------+-----------+

First I thought I'll deal with this easily using map having the letters as keys. This is really easy. However, map items don't have an order hence can't be sorted.

I guess I could deal with this using a structure:

type Letter struct {
    Value string
    Score int
}
type LetterList []Letter

However that brings bunch of other problems:

I need to check if the Letter is not already present in LetterList because I can't use the letters as keys
There's no direct way to sort them (using Int.sort() or so)

Using the structures just doesn't feel elegant at all. Is there a better solution?

假设我有一个字符串，我想计算每个字母的频率，然后按频率对表格进行排序。所需的“ hello larry”输出为： p>

  + -------- + ----------- + 
 | 信| 出现| 
 + -------- + ----------- + 
 |  l |  3 | 
 |  r |  2 | 
 |  h |  1 | 
 |  e |  1 | 
 |  o |  1 | 
 | 一个|  1 | 
 |  y |  1 | 
 + -------- + ----------- + 
  code>  pre> 
 
 首先，我想我会处理 使用以字母为键的 map  em>可以轻松实现这一点。 这真的很容易。 但是，地图 em>项目没有下订单 因此无法排序。 p> 
 
 
我想我可以使用以下结构进行处理： p> 
 
 

  type字母struct {
值 字符串
分数int 
} 
类型LetterList []字母
  code>  pre> 
 
 但是，这会带来很多其他问题： p> 
 
 

我需要检查Letter中是否不存在Letter，因为我不能将字母用作键 li> 
 
没有直接方法可以对它们进行排序（使用Int.sort（  ）左右） li> 
  ol> 
 
 使用这些结构根本感觉并不优雅。 有更好的解决方案吗？ p> 
  div>

答

You would be surprised how fast and efficient looping over a small slice is, and you can implement sorting on top of it fairly simple.

I recommend reading http://golang.org/pkg/sort/ SortWrapper.

type Letter struct {
    Value rune
    Score int
}

type LetterList []*Letter

func (ll *LetterList) FindOrAdd(r rune) (l *Letter) {
    for _, l = range *ll {
        if l.Value == r {
            return
        }
    }
    l = &Letter{Value: r, Score: 0}
    *ll = append(*ll, l)
    return
}

func (ll LetterList) SortByScore() LetterList {
    sort.Sort(llByScore{ll})
    return ll
}

func (ll LetterList) SortByValue() LetterList {
    sort.Sort(llByValue{ll})
    return ll
}

func (ll LetterList) String() string {
    var b bytes.Buffer
    b.WriteByte('[')
    for _, v := range ll {
        b.WriteString(fmt.Sprintf("{%q, %d}, ", v.Value, v.Score))
    }
    b.WriteByte(']')
    return b.String()

}

func New(s string) (ll LetterList) {
    ll = LetterList{}
    for _, r := range s {
        ll.FindOrAdd(r).Score++
    }
    return
}

func (ll LetterList) Len() int      { return len(ll) }
func (ll LetterList) Swap(i, j int) { ll[i], ll[j] = ll[j], ll[i] }

type llByScore struct{ LetterList }

func (l llByScore) Less(i, j int) bool {
    return l.LetterList[i].Score > l.LetterList[j].Score
}

type llByValue struct{ LetterList }

func (l llByValue) Less(i, j int) bool {
    return l.LetterList[i].Value > l.LetterList[j].Value
}

func main() {
    ll := New(`Let's say I have a string and I would like to count each letter's frequency and then sort the table by the frequency. Desired output of "hello larry" would be`)
    fmt.Println(ll)
    fmt.Println(ll.SortByScore())
    fmt.Println(ll.SortByValue())
}

playground

Another approach is to use a map then for sorting generate a list out of it and sort it.

如果无法使用Go lang对地图进行排序，那么正确的方法是什么？

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