题解 | #字符个数统计#

使用排序和堆栈去重

import java.util.*;
public class Main{
    public static void main(String [] args){
        getCharCount();
    }
    public static void getCharCount(){
        Scanner scan = new Scanner(System.in);
        String input = scan.nextLine();
        char [] ch = input.toCharArray();
        LinkedList<Character> list = new LinkedList<>();
        Arrays.sort(ch);
        for(int i = 0; i < ch.length; i ++){
            if(null == list || list.size() == 0 || list.getFirst() != ch[i]){
                list.push(ch[i]);
            }
        }
        System.out.print(list.size());
    }

}