Add problem 2002: Maximum Product of the Length of Two Palindromic Su…

…bsequences

src/lib.rs

@@ -1472,6 +1472,7 @@ pub mod problem_1995_count_special_quadruplets;
 pub mod problem_1996_the_number_of_weak_characters_in_the_game;
 pub mod problem_2000_reverse_prefix_of_word;
 pub mod problem_2001_number_of_pairs_of_interchangeable_rectangles;
+pub mod problem_2002_maximum_product_of_the_length_of_two_palindromic_subsequences;
 pub mod problem_2006_count_number_of_pairs_with_absolute_difference_k;
 pub mod problem_2007_find_original_array_from_doubled_array;
 pub mod problem_2011_final_value_of_variable_after_performing_operations;

src/problem_2002_maximum_product_of_the_length_of_two_palindromic_subsequences/dynamic_programming.rs

@@ -0,0 +1,51 @@
+pub struct Solution;
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl Solution {
+    pub fn max_product(s: String) -> i32 {
+        let s = s.as_bytes();
+        let n = s.len();
+        let mut cache = vec![0_u8; 1 << n].into_boxed_slice();
+        let full_mask = cache.len() - 1;
+
+        for mask in 1..cache.len() {
+            cache[mask] = if mask.is_power_of_two() {
+                1
+            } else {
+                let first_index = mask.trailing_zeros();
+                let last_index = usize::BITS - 1 - mask.leading_zeros();
+
+                if s[first_index as usize] == s[last_index as usize] {
+                    cache[mask ^ (1 << first_index) ^ (1 << last_index)] + 2
+                } else {
+                    cache[mask ^ (1 << first_index)].max(cache[mask ^ (1 << last_index)])
+                }
+            };
+        }
+
+        let mut result = 0_u8;
+
+        for mask in 1..=(full_mask >> 1) {
+            result = result.max(cache[mask] * cache[full_mask ^ mask]);
+        }
+
+        i32::from(result)
+    }
+}
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl super::Solution for Solution {
+    fn max_product(s: String) -> i32 {
+        Self::max_product(s)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_solution() {
+        super::super::tests::run::<super::Solution>();
+    }
+}

src/problem_2002_maximum_product_of_the_length_of_two_palindromic_subsequences/mod.rs

@@ -0,0 +1,18 @@
+pub mod dynamic_programming;
+
+pub trait Solution {
+    fn max_product(s: String) -> i32;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Solution;
+
+    pub fn run<S: Solution>() {
+        let test_cases = [("leetcodecom", 9), ("bb", 1), ("accbcaxxcxx", 25)];
+
+        for (s, expected) in test_cases {
+            assert_eq!(S::max_product(s.to_string()), expected);
+        }
+    }
+}