AtCoder Beginner Contest 275 D（2）

https://atcoder.jp/contests/abc275/tasks/abc275_d

構造体にメモを置けばそんなに気持ち悪くないと思います。

// Yet Another Recursive Function
#![allow(non_snake_case)]

use std::collections::HashMap;

fn read<T: std::str::FromStr>() -> T {
    let mut line = String::new();
    std::io::stdin().read_line(&mut line).ok();
    line.trim().parse().ok().unwrap()
}

struct RecursiveFunction {
    memo: HashMap<usize, usize>
}

impl RecursiveFunction {
    fn calc(&mut self, N: usize) -> usize {
        match self.memo.get(&N) {
            Some(&y) => y,
            None     => {
                let y = self.calc(N/2) + self.calc(N/3);
                self.memo.insert(N, y);
                y
            }
        }
    }
    
    fn create() -> RecursiveFunction {
        let mut memo = HashMap::<usize, usize>::new();
        memo.insert(0, 1);
        RecursiveFunction { memo }
    }
}

fn main() {
    let mut r = RecursiveFunction::create();
    let N = read();
    println!("{}", r.calc(N))
}