atcoder_acc_util.rs

mod acc_util{
    pub struct Accum{
        acc: Vec<i64>
    }

    impl Accum{
        pub fn new(a: &Vec<i64>) -> Accum{
            let mut acc: Vec<i64> = vec![];
            let mut s = 0;
            for i in a{
                s += *i;
                acc.push(s);
            }
            
            Accum{acc}
        }

        pub fn get(&self, l: usize, r: usize) -> i64{
            let mut l = l;
            let mut r = r;
            r = r.min(self.acc.len());
            l = l.max(0);
            if r <= l{
                return 0;
            }
            return self.acc[r - 1] - (if l == 0 {0} else {self.acc[l - 1]});
        }
    }

    #[test]
    fn test(){
        let x = vec![1, 10, 100, 1000];
        let a = Accum::new(&x);
        assert_eq!(a.get(0, 4), 1111);
        assert_eq!(a.get(1, 2), 10);
        assert_eq!(a.get(1, 3), 110);
    }

}