Rust 沒官方標準支援 gcd 跟 lcm 的 traits 蠻令人意外的

今天在練習 2197. Replace Non-Coprime Numbers in Array 時，需要使用到 GCD 跟 LCM，在 C++/Python 都有官方支援，Rust 跟 Go 都沒有支援，有點意外。

impl Solution {
    pub fn replace_non_coprimes(nums: Vec<i32>) -> Vec<i32> {
        let mut arr = Vec::with_capacity(nums.len());
        let mut curr = nums[0];
        let gcd = |mut a: i32, mut b: i32| -> i32 {
            if a < b {
                (a, b) = (b, a);
            }
            while b != 0 {
                (a, b) = (b, a % b);
            }
            a
        };
        let lcm = |a: i32, b: i32| -> i32 {
            a / gcd(a, b) * b
        };
        for &num in &nums[1..] {
            if gcd(num, curr) > 1 {
                curr = lcm(num, curr);
                while let Some(&last) = arr.last() && gcd(curr, last) > 1 {
                    curr = lcm(last, curr);
                    arr.pop();
                }
            } else {
                arr.push(curr);
                curr = num;
            }
        }
        arr.push(curr);
        arr
    }
}

這裡還剛好可以使用到 Rust 1.88 版本才開始有支援的 Let chains，Let chains 讓程式碼的表示更直白，真是太棒了。

if let Channel::Stable(v) = release_info()
    && let Semver { major, minor, .. } = v
    && major == 1
    && minor == 88
{
    println!("`let_chains` was stabilized in this version");
}