Sort Map(golang)

sortmap.go

package main

// sort a map's keys in descending order of its values.

import "sort"

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
}

您好，不是说map是无序的吗？怎么还可以进行排序？？

Note that slightly rewriting the Less method as follow ensure a deterministic sorting:

func (sm *sortedMap) Less(i, j int) bool {
    a, b := sm.m[sm.s[i]], sm.m[sm.s[j]]
    if a != b {
        // Order by decreasing value.
        return a > b
    } else {
        // Otherwise, alphabetical order.
        return sm.s[j] > sm.s[i]
    }
}