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2 years ago
type LS = Vec<Vec<Option<u64>>>;
struct Lattice { ls: LS }
impl Lattice {
pub fn new() -> Lattice {
let mut ls = LS::new();
for _i in 0..21 {
let lr = vec![None; 21];
ls.push(lr);
}
ls[0][0] = Some(1);
Lattice { ls: ls }
}
pub fn compute(&mut self, i: usize, j: usize) -> u64 {
if self.ls[i][j].is_some() { return self.ls[i][j].unwrap(); }
let mut res = 0u64;
if i > 0 { res += self.compute(i - 1, j); }
if j > 0 { res += self.compute(i, j - 1); }
self.ls[i][j] = Some(res);
res
}
}
fn main() {
let mut lt = Lattice::new();
let res = lt.compute(20, 20);
println!("{}", res);
}