如何在 Rust 中将 u32 数据类型转换为 bigInt？

Question

I am doing Fibonacci sequence function and the return type should return BigUint type. I search through many webs but I couldn't find the site that show the way. This is my process so far.

pub fn fibo_seq(n: u32) -> Vec<num_bigint::BigUint> {
    let mut f1 = 0;
    let mut temp = 1;
    let mut f2 = 1;
    let mut vec:Vec<u32> = Vec::new();

    while vec.len() < n.try_into().unwrap(){
       vec.push(f2);
       temp = f2;
       f2 = f1 + f2;
       f1 = temp;  

    }

    vec // return wrong data type

}

Answer 1

You can't just put BigUint in the return type, you have to actually use it!

pub fn fibo_seq(n: u32) -> Vec<BigUint> {
    let mut f1 = BigUint::from(0u32);
    let mut temp = BigUint::from(1u32);
    let mut f2 = BigUint::from(1u32);
    let mut vec: Vec<BigUint> = Vec::new();

    while vec.len() < n.try_into().unwrap(){
       vec.push(f2.clone());
       temp = f2.clone();
       f2 = f1 + &f2;
       f1 = temp;  

    }

    vec
}

Answer 2

Since you are return Vec<BigUint> you need Vec<BigUint> instead of Vec<u32> .

To improve you can rewrite the same method without temp variable as below.

use num_bigint::BigUint;

pub fn fibo_seq(n: u32) -> Vec<BigUint> {
    let mut f1 = BigUint::from(0u32);
    let mut f2 = BigUint::from(1u32);
    let mut vec:Vec<BigUint> = Vec::new();

    while vec.len() < n.try_into().unwrap() {
       (f2, f1) = (f1 + &f2, f2);
       vec.push(f1.clone());
    }

    vec
}