Method two_sum

1. Two Sum/src/main.rs:8–19

(nums: Vec<i32>, target: i32)

impl Solution {
    pub fn two_sum(nums: Vec<i32>, target: i32) -> Vec<i32> {
        use std::collections::HashMap;
        let mut map: HashMap<i32, i32> = HashMap::new();
        for i in 0..nums.len() {
            let pair = target - nums[i];
            match map.get(&pair) {
                None => { map.insert(nums[i], i as i32); }
                Some(&idx) => { return vec![idx, i as i32] }
            }
        }
        unimplemented!()
    }
}

#[cfg(test)]