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September 29, 2020 01:34
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A translation from Ruby to Rust in the book :pp.013-017[「もっとプログラマ脳を鍛える数学パズル」](https://www.shoeisha.co.jp/book/detail/9784798153612)
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use std::collections::HashMap; | |
struct Checker { | |
memo: HashMap<(i64, i64), i64>, | |
max_seat_at_one_table: i64, | |
} | |
impl Checker { | |
pub fn check(&mut self, remain: i64, pre: i64) -> i64 { | |
match &self.memo.get(&(remain, pre)) { | |
Some(cnt) => return **cnt, | |
_ => { | |
if remain < 0 { | |
return 0; | |
} else if remain == 0 { | |
return 1; | |
} else { | |
let mut count = 0; | |
for i in pre..=self.max_seat_at_one_table { | |
count += self.check(remain - i, i); | |
} | |
&self.memo.insert((remain, pre), count); | |
return count; | |
} | |
} | |
} | |
} | |
} | |
fn main() { | |
let mut chk = Checker { | |
memo: HashMap::new(), | |
max_seat_at_one_table: 10, | |
}; | |
println!("{}", chk.check(100, 2)); | |
} | |
#[cfg(test)] | |
mod tests { | |
use super::*; | |
#[test] | |
fn test_check() { | |
let number_of_people = 100; | |
let mut chk = Checker { | |
memo: HashMap::new(), | |
max_seat_at_one_table: 10, | |
}; | |
assert_eq!(chk.check(number_of_people, 2), 437_420); | |
} | |
} |
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