dsalgo 0.3.10

A package for Datastructures and Algorithms.
Documentation 
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pub trait Monoid {
    type T;

    fn op(
        &self,
        l: Self::T,
        r: Self::T,
    ) -> Self::T;

    fn e(&self) -> Self::T;
}

pub struct DualSegtree<G: Monoid> {
    g: G,
    node: Vec<G::T>,
    size: usize,
}

impl<G: Monoid> DualSegtree<G>
where
    G::T: Clone,
{
    pub fn new(
        g: G,
        size: usize,
    ) -> Self {
        assert!(size > 0);

        let n = size.next_power_of_two();

        let node = vec![g.e(); n << 1];

        Self { g, node, size }
    }

    pub fn size(&self) -> usize {
        self.size
    }

    fn n(&self) -> usize {
        self.node.len() >> 1
    }

    fn operate_node(
        &mut self,
        i: usize,
        x: G::T,
    ) {
        self.node[i] = self.g.op(self.node[i].clone(), x);
    }

    fn propagate(
        &mut self,
        i: usize,
    ) {
        self.operate_node(i << 1, self.node[i].clone());

        self.operate_node(i << 1 | 1, self.node[i].clone());

        self.node[i] = self.g.e();
    }

    pub fn get(
        &mut self,
        i: usize,
    ) -> &mut G::T {
        assert!(i < self.size());

        self._get(i, 0, self.n(), 1)
    }

    fn _get(
        &mut self,
        i: usize,
        cl: usize,
        cr: usize,
        ci: usize,
    ) -> &mut G::T {
        assert!(cl <= i && i < cr);

        if cr - cl == 1 {
            return &mut self.node[ci];
        }

        self.propagate(ci);

        let c = (cl + cr) >> 1;

        if i < c {
            self._get(i, cl, c, ci << 1)
        } else {
            self._get(i, c, cr, ci << 1 | 1)
        }
    }

    pub fn operate(
        &mut self,
        l: usize,
        r: usize,
        x: G::T,
    ) {
        assert!(l <= r && r <= self.size);

        self._operate(l, r, 0, self.n(), 1, x);
    }

    fn _operate(
        &mut self,
        l: usize,
        r: usize,
        cl: usize,
        cr: usize,
        i: usize,
        x: G::T,
    ) {
        if cr <= l || r <= cl {
            return;
        }

        if l <= cl && cr <= r {
            self.operate_node(i, x);

            return;
        }

        self.propagate(i);

        let c = (cl + cr) >> 1;

        self._operate(l, r, cl, c, i << 1, x.clone());

        self._operate(l, r, c, cr, i << 1 | 1, x.clone());
    }
}

#[cfg(test)]

mod tests {

    use super::*;

    #[test]

    fn test() {
        struct M;

        impl Monoid for M {
            type T = i64;

            fn op(
                &self,
                l: Self::T,
                r: Self::T,
            ) -> Self::T {
                l + r
            }

            fn e(&self) -> Self::T {
                0
            }
        }

        let n = 5;

        let mut seg = DualSegtree::new(M {}, n);

        seg.operate(1, 3, 1);

        assert_eq!(seg.get(0), &0);

        assert_eq!(seg.get(1), &1);

        assert_eq!(seg.get(1), &1);

        assert_eq!(seg.get(0), &0);

        assert_eq!(seg.get(0), &0);

        *seg.get(0) = -1;

        seg.operate(0, 2, -1);

        assert_eq!(seg.get(0), &-2);

        assert_eq!(seg.get(1), &0);

        assert_eq!(seg.get(2), &1);
    }
}