数列 - 遅延伝播セグメントツリー (遅延セグ木)

/// Sequence - Lazy Segment Tree
use crate::algebra::act::*;
use crate::algebra::monoid::*;

#[derive(Debug, Clone)]
pub struct LazySegmentTree<X, M> {
    length: usize,       // of leaves
    length_upper: usize, // power of 2
    size: usize,         // of nodes
    data: Vec<X>,
    act: Vec<M>,
}
impl<X: Copy + Monoid, M: Copy + Monoid + Act<X>> LazySegmentTree<X, M> {
    pub fn new(length: usize) -> Self {
        let mut length_upper = 1;
        while length_upper < length {
            length_upper *= 2;
        }
        let size = length_upper * 2 - 1;
        let data = vec![X::unit(); size];
        let act = vec![M::unit(); size];
        LazySegmentTree {
            length,
            length_upper,
            size,
            data,
            act,
        }
    }
    pub fn from(xs: Vec<X>) -> Self {
        let mut tree = Self::new(xs.len());
        for i in 0..xs.len() {
            tree.data[tree.size / 2 + i] = xs[i];
        }
        for i in (0..tree.size / 2).rev() {
            tree.data[i] = tree.data[2 * i + 1] * tree.data[2 * i + 2];
        }
        tree
    }
    fn propagation(&mut self, idx: usize) {
        if idx < self.size / 2 {
            self.act[idx * 2 + 1] = self.act[idx * 2 + 1] * self.act[idx];
            self.act[idx * 2 + 2] = self.act[idx * 2 + 2] * self.act[idx];
        }
        self.data[idx] = self.act[idx].act(self.data[idx]);
        self.act[idx] = M::unit();
    }
    fn update_sub(
        &mut self,
        range: std::ops::Range<usize>,
        m: M,
        idx: usize,
        focus: std::ops::Range<usize>,
    ) {
        self.propagation(idx);
        if focus.end <= range.start || range.end <= focus.start {
            return;
        }
        if range.start <= focus.start && focus.end <= range.end {
            self.act[idx] = self.act[idx] * m;
            self.propagation(idx);
        } else if idx < self.data.len() / 2 {
            let mid = (focus.start + focus.end) / 2;
            self.update_sub(range.clone(), m, idx * 2 + 1, focus.start..mid);
            self.update_sub(range.clone(), m, idx * 2 + 2, mid..focus.end);
            self.data[idx] = self.data[idx * 2 + 1] * self.data[idx * 2 + 2];
        }
    }
    pub fn update(&mut self, range: std::ops::Range<usize>, m: M) {
        self.update_sub(range, m, 0, 0..self.length_upper);
    }
    fn product_sub(
        &mut self,
        range: std::ops::Range<usize>,
        idx: usize,
        focus: std::ops::Range<usize>,
    ) -> X {
        self.propagation(idx);
        if focus.end <= range.start || range.end <= focus.start {
            X::unit()
        } else if range.start <= focus.start && focus.end <= range.end {
            self.data[idx]
        } else {
            let mid = (focus.start + focus.end) / 2;
            let a = self.product_sub(range.clone(), idx * 2 + 1, focus.start..mid);
            let b = self.product_sub(range.clone(), idx * 2 + 2, mid..focus.end);
            a * b
        }
    }
    pub fn product(&mut self, range: std::ops::Range<usize>) -> X {
        self.product_sub(range, 0, 0..self.length_upper)
    }
    pub fn index(&mut self, i: usize) -> X {
        self.product(i..i + 1)
    }
    pub fn to_vec(&mut self) -> Vec<X> {
        (0..self.length).map(|i| self.index(i)).collect()
    }
}
impl<X: std::fmt::Debug, M: std::fmt::Debug> LazySegmentTree<X, M> {
    pub fn debug(&self) {
        #[cfg(debug_assertions)]
        for i in 0..self.size {
            if i > 0 && (i + 1).count_ones() == 1 {
                eprintln!();
            }
            eprint!("{:?} / {:?}; ", &self.data[i], &self.act[i]);
        }
        eprintln!();
    }
}