题解 | #字符个数统计#

经典的思路

public class Main{
    public static void main(String[] args){
        Scanner scan = new Scanner(System.in);
        String str = scan.nextLine();
        int[] count = new int[129];
        for(char c : str.toCharArray()){
            count[c]++;
        }
        int sum = 0;
        for(int i : count){
            if(i>0){
                sum++;
            }
        }
        System.out.println(sum);
    }
}