fn sum_of_vector_1(v: &Vec<i32>, n: i32) -> i32 {
    let mut sum = 0;
    for i in v {
        sum = sum + i * n;
    }
    sum
}

fn sum_of_vector_2(v: &Vec<i32>, n: i32) -> i32 {
    v.iter()
     .map(|i| i * n)
     .fold(0, |acc, x| acc + x)
}

fn main() {
    let v = vec![2, 4, 5, 6, 7];
    let n = 1;
    assert_eq!(sum_of_vector_1(&v, n), sum_of_vector_2(&v, n));
}