use std::cmp::Ordering;

impl Solution {
    pub fn search(mut nums: Vec<i32>, target: i32) -> i32 {
        // nums.len() > 0 so this is safe to do
        if *nums.first().unwrap_or(&-target) == target {
            return 0;
        }
        let mut current = nums.as_slice();
        let mut idx = 0;
        while current.len() > 1 {
            let m = current.len() / 2;
            match target.cmp(&current[m]) {
                Ordering::Equal => return (idx + m) as i32,
                Ordering::Greater => {
                    current = current.split_at(m).1;
                    idx += m;
                },
                Ordering::Less => current = current.split_at(m).0
            }
        }
        -1
    }
}