Add problem 2382: Maximum Segment Sum After Removals

Author: EFanZh

src/lib.rs

@@ -1772,6 +1772,7 @@ pub mod problem_2375_construct_smallest_number_from_di_string;
 pub mod problem_2379_minimum_recolors_to_get_k_consecutive_black_blocks;
 pub mod problem_2380_time_needed_to_rearrange_a_binary_string;
 pub mod problem_2381_shifting_letters_ii;
+pub mod problem_2382_maximum_segment_sum_after_removals;
 
 #[cfg(test)]
 mod test_utilities;

src/problem_2382_maximum_segment_sum_after_removals/mod.rs

@@ -0,0 +1,35 @@
+pub mod reversed_iteration;
+
+pub trait Solution {
+    fn maximum_segment_sum(nums: Vec<i32>, remove_queries: Vec<i32>) -> Vec<i64>;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Solution;
+
+    pub fn run<S: Solution>() {
+        let test_cases = [
+            (
+                (&[1, 2, 5, 6, 1] as &[_], &[0, 3, 2, 4, 1] as &[_]),
+                &[14_i64, 7, 2, 2, 0] as &[_],
+            ),
+            ((&[3, 2, 11, 1], &[3, 2, 1, 0]), &[16, 5, 3, 0]),
+            (
+                (
+                    &[
+                        244, 19, 445, 671, 801, 103, 291, 335, 781, 33, 51, 789, 746, 510, 38, 7, 529, 905,
+                    ],
+                    &[4, 8, 11, 12, 1, 5, 0, 9, 6, 17, 3, 15, 14, 7, 2, 13, 16, 10],
+                ),
+                &[
+                    5118, 3608, 2735, 1989, 1989, 1989, 1989, 1989, 1989, 1116, 1084, 548, 529, 529, 529, 529, 51, 0,
+                ],
+            ),
+        ];
+
+        for ((nums, remove_queries), expected) in test_cases {
+            assert_eq!(S::maximum_segment_sum(nums.to_vec(), remove_queries.to_vec()), expected);
+        }
+    }
+}

src/problem_2382_maximum_segment_sum_after_removals/reversed_iteration.rs

@@ -0,0 +1,99 @@
+pub struct Solution;
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+use std::cell::Cell;
+use std::iter;
+
+struct Item {
+    end_index: Cell<usize>,
+    sum: Cell<u64>,
+}
+
+impl Solution {
+    fn filter(item: &Item) -> Option<(&Item, u64)> {
+        let item_sum = item.sum.get();
+
+        (item_sum != 0).then_some((item, item_sum))
+    }
+
+    pub fn maximum_segment_sum(nums: Vec<i32>, remove_queries: Vec<i32>) -> Vec<i64> {
+        let n = remove_queries.len();
+
+        let items = iter::repeat_with(|| Item {
+            sum: Cell::new(0),
+            end_index: Cell::new(0),
+        })
+        .take(n)
+        .collect::<Box<_>>();
+
+        let mut result = vec![0; n];
+        let mut max_sum = 0;
+
+        result
+            .iter_mut()
+            .zip(&remove_queries)
+            .rev()
+            .for_each(|(target, &index)| {
+                *target = max_sum as _;
+
+                let mut index = index as u32 as usize;
+                let mut end = &items[index];
+                let mut sum = u64::from(nums[index] as u32);
+                let other_end;
+
+                'block: {
+                    let (other, other_sum) = match (
+                        items.get(index.wrapping_sub(1)).and_then(Self::filter),
+                        items.get(index + 1).and_then(Self::filter),
+                    ) {
+                        (None, None) => {
+                            other_end = end;
+
+                            break 'block;
+                        }
+                        (None, Some((other, other_sum))) | (Some((other, other_sum)), None) => (other, other_sum),
+                        (Some((left, left_sum)), Some((right, right_sum))) => {
+                            index = left.end_index.get();
+                            end = &items[index];
+                            sum += left_sum;
+
+                            (right, right_sum)
+                        }
+                    };
+
+                    let other_end_index = other.end_index.get();
+
+                    other_end = &items[other_end_index];
+
+                    sum += other_sum;
+
+                    end.end_index.set(other_end_index);
+                    end.sum.set(sum);
+                }
+
+                other_end.end_index.set(index);
+                other_end.sum.set(sum);
+
+                max_sum = max_sum.max(sum);
+            });
+
+        result
+    }
+}
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl super::Solution for Solution {
+    fn maximum_segment_sum(nums: Vec<i32>, remove_queries: Vec<i32>) -> Vec<i64> {
+        Self::maximum_segment_sum(nums, remove_queries)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_solution() {
+        super::super::tests::run::<super::Solution>();
+    }
+}