Deque with aggregate (#93)

* saving

* progress

* now ACs

* finish

* rename

* finish docs

* add source

* nit

---------

Co-authored-by: Luke Videckis <[email protected]>
Co-authored-by: Cameron Custer <[email protected]>

Cargo.toml

@@ -224,6 +224,10 @@ path = "examples/monotonic/count_rects.rs"
 name = "cartesian_tree"
 path = "examples/monotonic/cartesian_tree.rs"
 
+[[example]]
+name = "deq_agg"
+path = "examples/data_structures/deq_agg.rs"
+
 [[example]]
 name = "fenwick_kth"
 path = "examples/data_structures/fenwick_kth.rs"
@@ -238,4 +242,4 @@ path = "examples/graphs/lca_rmq_next_on_path.rs"
 
 [[example]]
 name = "linear_rmq"
-path = "examples/data_structures/linear_rmq.rs"
+path = "examples/data_structures/linear_rmq.rs"

examples/data_structures/deq_agg.rs

@@ -0,0 +1,71 @@
+// verification-helper: PROBLEM https://judge.yosupo.jp/problem/deque_operate_all_composite
+
+use proconio::input;
+use programming_team_code_rust::data_structures::deq_agg::DeqAgg;
+use rand::{thread_rng, Rng};
+use std::collections::VecDeque;
+
+const MOD: u64 = 998_244_353;
+
+fn main() {
+    let mut rng = thread_rng();
+    input! {
+        q: usize,
+    }
+
+    let mut std_deq = VecDeque::new();
+    let mut deq =
+        DeqAgg::new(|&i: &(u64, u64), &j: &(u64, u64)| (i.0 * j.0 % MOD, (j.0 * i.1 + j.1) % MOD));
+
+    for _ in 0..q {
+        input! {
+            t: u8,
+        }
+        match t {
+            0 => {
+                input! {
+                    a: u64,
+                    b: u64,
+                }
+                deq.push_front((a, b));
+                std_deq.push_front((a, b));
+            }
+            1 => {
+                input! {
+                    a: u64,
+                    b: u64,
+                }
+                deq.push_back((a, b));
+                std_deq.push_back((a, b));
+            }
+            2 => {
+                deq.pop_front();
+                std_deq.pop_front();
+            }
+            3 => {
+                deq.pop_back();
+                std_deq.pop_back();
+            }
+            _ => {
+                input! {
+                    x: u64,
+                }
+                if let Some((a, b)) = deq.query() {
+                    println!("{}", (a * x + b) % MOD);
+                } else {
+                    println!("{}", x);
+                }
+            }
+        }
+        assert_eq!(deq.len(), std_deq.len());
+        assert_eq!(deq.is_empty(), std_deq.is_empty());
+        assert_eq!(deq.front(), std_deq.front());
+        assert_eq!(deq.back(), std_deq.back());
+        if !std_deq.is_empty() {
+            for _ in 0..3 {
+                let i = rng.gen_range(0..deq.len());
+                assert_eq!(deq[i], std_deq[i]);
+            }
+        }
+    }
+}

src/data_structures/deq_agg.rs

@@ -0,0 +1,201 @@
+//! # Deque with Aggregate
+
+/// - see <https://github.com/suisen-cp/cp-library-cpp/blob/main/library/datastructure/deque_aggregation.hpp>
+///
+/// simulate a deque with 2 stacks:
+/// `le`, `ri` are stacks of { number, sum }
+///     accumulate
+///    <-----------  -------> fold numbers from inside
+///   (     le     ][  ri    )
+///
+/// # Example
+/// ```
+/// use programming_team_code_rust::data_structures::deq_agg::DeqAgg;
+///
+/// let mut deq = DeqAgg::new(|&x, &y| std::cmp::max(x, y));
+/// deq.push_front(5);
+/// deq.push_front(3);
+/// deq.push_back(1);
+/// assert_eq!(deq[1], 5);
+/// assert!(std::panic::catch_unwind(|| deq[3]).is_err());
+/// assert_eq!(deq.query(), Some(5));
+/// assert_eq!(deq.front(), Some(&3));
+/// assert_eq!(deq.pop_front(), Some(3));
+/// assert_eq!(deq.back(), Some(&1));
+/// assert_eq!(deq.pop_back(), Some(1));
+/// ```
+pub struct DeqAgg<T, F> {
+    le: Vec<(T, T)>,
+    ri: Vec<(T, T)>,
+    op: F,
+}
+
+impl<T: Clone, F: Fn(&T, &T) -> T> DeqAgg<T, F> {
+    /// Creates new instance of DeqAgg
+    ///
+    /// # Complexity
+    /// - Time: O(1)
+    /// - Space: O(1)
+    pub fn new(op: F) -> Self {
+        Self {
+            le: vec![],
+            ri: vec![],
+            op,
+        }
+    }
+
+    /// # Complexity
+    /// - Time: O(1)
+    /// - Space: O(1)
+    pub fn len(&self) -> usize {
+        self.le.len() + self.ri.len()
+    }
+
+    /// # Complexity
+    /// - Time: O(1)
+    /// - Space: O(1)
+    pub fn is_empty(&self) -> bool {
+        self.le.is_empty() && self.ri.is_empty()
+    }
+
+    /// Gets deq\[0\] op deq\[1\] op ... op deq.back(); or None if empty
+    ///
+    /// # Complexity
+    /// - Time: O(1)
+    /// - Space: O(1)
+    pub fn query(&self) -> Option<T> {
+        if self.is_empty() {
+            None
+        } else if self.le.is_empty() {
+            Some(self.ri.last().unwrap().1.clone())
+        } else if self.ri.is_empty() {
+            Some(self.le.last().unwrap().1.clone())
+        } else {
+            Some((self.op)(
+                &self.le.last().unwrap().1,
+                &self.ri.last().unwrap().1,
+            ))
+        }
+    }
+
+    /// Gets deq\[0\]; or None if empty
+    ///
+    /// # Complexity
+    /// - Time: O(1)
+    /// - Space: O(1)
+    pub fn front(&self) -> Option<&T> {
+        if let Some(last) = self.le.last() {
+            Some(&last.0)
+        } else if !self.ri.is_empty() {
+            Some(&self.ri[0].0)
+        } else {
+            None
+        }
+    }
+
+    /// Gets deq\[deq.len() - 1\]; or None if empty
+    ///
+    /// # Complexity
+    /// - Time: O(1)
+    /// - Space: O(1)
+    pub fn back(&self) -> Option<&T> {
+        if let Some(last) = self.ri.last() {
+            Some(&last.0)
+        } else if !self.le.is_empty() {
+            Some(&self.le[0].0)
+        } else {
+            None
+        }
+    }
+
+    /// # Complexity
+    /// - Time: O(1)
+    /// - Space: O(1)
+    pub fn push_front(&mut self, elem: T) {
+        self.le.push((
+            elem.clone(),
+            if let Some(last) = self.le.last() {
+                (self.op)(&elem, &last.1)
+            } else {
+                elem
+            },
+        ));
+    }
+
+    /// # Complexity
+    /// - Time: O(1)
+    /// - Space: O(1)
+    pub fn push_back(&mut self, elem: T) {
+        self.ri.push((
+            elem.clone(),
+            if let Some(last) = self.ri.last() {
+                (self.op)(&last.1, &elem)
+            } else {
+                elem
+            },
+        ));
+    }
+
+    /// Removes front, and returns it; or None if empty
+    ///
+    /// # Complexity
+    /// - Time: O(1) ammortized
+    /// - Space: O(1) ammortized
+    pub fn pop_front(&mut self) -> Option<T> {
+        if self.le.is_empty() {
+            let mut ary = vec![];
+            std::mem::swap(&mut ary, &mut self.ri);
+            self.rebuild((ary.len() + 1) / 2, ary);
+        }
+        self.le.pop().map(|elem| elem.0)
+    }
+
+    /// Removes back, and returns it; or None if empty
+    ///
+    /// # Complexity
+    /// - Time: O(1) ammortized
+    /// - Space: O(1) ammortized
+    pub fn pop_back(&mut self) -> Option<T> {
+        if self.ri.is_empty() {
+            let mut ary = vec![];
+            std::mem::swap(&mut ary, &mut self.le);
+            ary.reverse();
+            self.rebuild(ary.len() / 2, ary);
+        }
+        self.ri.pop().map(|elem| elem.0)
+    }
+
+    fn rebuild(&mut self, le_len: usize, mut ary: Vec<(T, T)>) {
+        self.ri = ary.split_off(le_len);
+        self.le = ary;
+        self.le.reverse();
+        for i in 0..self.le.len() {
+            self.le[i].1 = if i == 0 {
+                self.le[0].0.clone()
+            } else {
+                (self.op)(&self.le[i].0, &self.le[i - 1].1)
+            };
+        }
+        for i in 0..self.ri.len() {
+            self.ri[i].1 = if i == 0 {
+                self.ri[0].0.clone()
+            } else {
+                (self.op)(&self.ri[i - 1].1, &self.ri[i].0)
+            };
+        }
+    }
+}
+
+/// # Complexity
+/// - Time: O(1)
+/// - Space: O(1)
+impl<T, F> std::ops::Index<usize> for DeqAgg<T, F> {
+    type Output = T;
+    fn index(&self, i: usize) -> &Self::Output {
+        if i < self.le.len() {
+            &self.le[self.le.len() - i - 1].0
+        } else {
+            &self.ri[i - self.le.len()].0
+        }
+    }
+}

src/data_structures/mod.rs

@@ -1,5 +1,6 @@
 //! # Data Structures
 pub mod binary_trie;
+pub mod deq_agg;
 pub mod disjoint_rmq;
 pub mod fenwick;
 pub mod lazy_seg_tree;