题解 | #计算某字符出现次数#

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

fn main() {
    let stdin = io::stdin();
    let mut lines = stdin.lock().lines();

    let mut input_string = lines.next().unwrap().unwrap();
    let mut target_char = lines.next().unwrap().unwrap();

    input_string = input_string.to_lowercase();
    let target_char = target_char.to_lowercase().chars().next().unwrap();

    print!("{}\n", input_string.chars().filter(|&c| c == target_char).count());
}