Golang 解法

如果只是打印出来的话，可以将dedup()中的res改成map来去重。

package main

import (
    "fmt"
)

func reserve(s string) (res string) {
    for _, v := range s {
        res = string(v) + res
    }
    return res
}

func dedup(s string) (res string) {
    for _, vs := range s {
        for _, vr := range res {
            if vs == vr {
                goto breakHere
            }
        }
        res += string(vs)
        breakHere:
    }
    return res
}

func main() {
    var s string
    fmt.Scanf("%s", &s)
    res := reserve(s)
    res = dedup(res)
    fmt.Println(res)
}