题解 | #字符个数统计#

HashSet来解

use std::io::{self, *};
use std::collections::HashSet;

fn main() {
    let stdin = io::stdin();
    let mut table = HashSet::new();
    for line in stdin.lock().lines() {
        let mut v : Vec<u8> = Vec::from(line.unwrap());
        for i in 0..v.len(){
            if v[i] < 128u8 {
                table.insert(v[i]);
            }
        }
        println!("{}",table.len());
    }
}

也可以辅助数组：

use std::io::{self, *};

fn main() {
    let stdin = io::stdin();
    let mut table = vec![0; 128];
    for line in stdin.lock().lines() {
        let mut v : Vec<u8> = Vec::from(line.unwrap());
        for i in 0..v.len(){
            if v[i] > 127u8 {
                
            }else if table[v[i] as usize] == 0 {
                table[v[i] as usize] += 1;
            }
        }
        let mut sum = 0i32;
        for i in 0..128 {
            if table[i] == 1 {sum += 1;}
        }
        println!("{}",sum);
        table = vec![0; 128];
    }
}