map 按value 大小排序，降序和升序。
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package main
import "fmt"
import "sort"
func main() {
m := map[string]int{
"One": 100,
"Two": 2,
"Three": 3,
"Ten": 10,
"Fifty": 50,
}
vs := NewValSorter(m)
fmt.Printf("%v\n", *vs)
vs.Sort()
fmt.Printf("%v\n", *vs)
}
type ValSorter struct {
Keys []string
Vals []int
}
func NewValSorter(m map[string]int) *ValSorter {
vs := &ValSorter{
Keys: make([]string, 0, len(m)),
Vals: make([]int, 0, len(m)),
}
for k, v := range m {
vs.Keys = append(vs.Keys, k)
vs.Vals = append(vs.Vals, v)
}
return vs
}
func (vs *ValSorter) Sort() {
sort.Sort(vs)
}
func (vs *ValSorter) Len() int { return len(vs.Vals) }
func (vs *ValSorter) Less(i, j int) bool { return vs.Vals[i] < vs.Vals[j] }
func (vs *ValSorter) Swap(i, j int) {
vs.Vals[i], vs.Vals[j] = vs.Vals[j], vs.Vals[i]
vs.Keys[i], vs.Keys[j] = vs.Keys[j], vs.Keys[i]
}
输出：
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{[One Two Three Ten Fifty] [100 2 3 10 50]}
{[Two Three Ten Fifty One] [2 3 10 50 100]}
这是按升序排序，如果要按降序排列则修改下面一行：
1func (vs *ValSorter) Less(i, j int) bool { return vs.Vals[i] > vs.Vals[j] }
下面另一种实现简单一些：
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package main
// sort a map's keys in descending order of its values.
import "sort"
import "fmt"
type sortedMap struct {
m map[string]int
s []string
}
func (sm *sortedMap) Len() int {
return len(sm.m)
}
func (sm *sortedMap) Less(i, j int) bool {
return sm.m[sm.s[i]] > sm.m[sm.s[j]]
}
func (sm *sortedMap) Swap(i, j int) {
sm.s[i], sm.s[j] = sm.s[j], sm.s[i]
}
func sortedKeys(m map[string]int) []string {
sm := new(sortedMap)
sm.m = m
sm.s = make([]string, len(m))
i := 0
for key, _ := range m {
sm.s[i] = key
i++
}
sort.Sort(sm)
return sm.s
}
func main() {
s := []string{"Python", "Python", "Python", "igor", "igor", "igor", "igor", "go", "go", "Golang", "Golang", "Golang", "Golang", "Py", "Py"}
count := make(map[string]int)
for _, v := range s {
count[v]++
}
for _, res := range sortedKeys(count) {
fmt.Println(res, count[res])
}
}
go1.8 后提供的 slice sort 功能使排序更简单：
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package main
import (
"fmt"
"sort"
)
func main() {
m := map[string]int{
"something": 10,
"yo": 20,
"blah": 20,
}
type kv struct {
Key string
Value int
}
var ss []kv
for k, v := range m {
ss = append(ss, kv{k, v})
}
sort.Slice(ss, func(i, j int) bool {
return ss[i].Value > ss[j].Value // 降序
// return ss[i].Value < ss[j].Value // 升序
})
for _, v := range ss {
fmt.Printf("%s, %d\n", v.Key, v.Value)
}
}
输出：
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3
yo, 20
blah, 20
something, 10
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