题解 | #计算某字符出现次数#

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

fn main() {
    let stdin = io::stdin();
    let mut strr=String::new();
    let mut aim=String::new();
    stdin.read_line(&mut strr).expect("faled");
    stdin.read_line(&mut aim).expect("faled");
    let low_strr=strr.to_lowercase();
    let ch=aim.to_lowercase().chars().next();
    if let Some(ch)=ch{
        let count=low_strr.matches(ch).count();
        //println!("{}",low_strr);
        println!("{}",count);
    }
   else{
    println!("invalid");
   }

}