Function fib_classic_iteration_loop

src/dp/fib.rs:36–56

(n: usize)

/// 只保存前两个值，最节省内存和最快的方式
#[allow(unused)]
pub fn fib_classic_iteration_loop(n: usize) -> usize {
    match n {
        0 => 0,
        1 | 2 => 1,
        _ => {
            let mut prev = 1;
            let mut cur = 1;
            let mut i = 3;
            loop {
                let sum = prev + cur;
                prev = cur;
                cur = sum;

                i += 1;
                if i > n {
                    return cur;
                }
            }
        }
    }
}

/// 只保存前两个值，最节省内存和最快的方式
/// 但实际基准测试结果并没有预期的那么快, 有可能是for的原因