Add problem 2370: Longest Ideal Subsequence

src/lib.rs

@@ -1763,6 +1763,7 @@ pub mod problem_2365_task_scheduler_ii;
 pub mod problem_2366_minimum_replacements_to_sort_the_array;
 pub mod problem_2367_number_of_arithmetic_triplets;
 pub mod problem_2368_reachable_nodes_with_restrictions;
+pub mod problem_2370_longest_ideal_subsequence;
 
 #[cfg(test)]
 mod test_utilities;

src/problem_2370_longest_ideal_subsequence/dynamic_programming.rs

@@ -0,0 +1,38 @@
+pub struct Solution;
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl Solution {
+    fn fold_max(s: &[u32]) -> u32 {
+        s.iter().fold(0, |max, &x| max.max(x))
+    }
+
+    pub fn longest_ideal_string(s: String, k: i32) -> i32 {
+        let k = k as u32 as usize;
+        let mut cache = [0_u32; 26];
+
+        for c in s.into_bytes() {
+            let c = usize::from(c - b'a');
+
+            cache[c] = Self::fold_max(&cache[c.saturating_sub(k)..=(c + k).min(25)]) + 1;
+        }
+
+        Self::fold_max(&cache) as _
+    }
+}
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl super::Solution for Solution {
+    fn longest_ideal_string(s: String, k: i32) -> i32 {
+        Self::longest_ideal_string(s, k)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_solution() {
+        super::super::tests::run::<super::Solution>();
+    }
+}

src/problem_2370_longest_ideal_subsequence/mod.rs

@@ -0,0 +1,18 @@
+pub mod dynamic_programming;
+
+pub trait Solution {
+    fn longest_ideal_string(s: String, k: i32) -> i32;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Solution;
+
+    pub fn run<S: Solution>() {
+        let test_cases = [(("acfgbd", 2), 4), (("abcd", 3), 4)];
+
+        for ((s, k), expected) in test_cases {
+            assert_eq!(S::longest_ideal_string(s.to_string(), k), expected);
+        }
+    }
+}