题解 | #字符统计#

package main

import (
	"fmt"
	"sort"
)

func main() {
    var str string
    fmt.Scan(&str)
    mp := make(map[rune]int)
    res := make([]rune, 0, 40)
    for _, item := range str {
        if _, ok := mp[item]; !ok {
            res = append(res, item)
        }
        mp[item]++
    }
    sort.Slice(res, func(i, j int) bool{
        if mp[res[i]] == mp[res[j]] {
            return res[i] < res[j]
        }
        return mp[res[i]] > mp[res[j]]
    })
    fmt.Println(string(res))
}