Method sum

677-map-sum-pairs.rs:28–36

(&mut self, prefix: String)

    }

    fn sum(&mut self, prefix: String) -> i32 {
        let mut ret = 0;
        for (k, v) in &self.mmp {
            if k.starts_with(&prefix) {
                ret += v;
            }
        }
        ret
    }
}

fn main() {