Add problem 2207: Maximize Number of Subsequences in a String

src/lib.rs

@@ -1625,6 +1625,7 @@ pub mod problem_2197_replace_non_coprime_numbers_in_array;
 pub mod problem_2200_find_all_k_distant_indices_in_an_array;
 pub mod problem_2202_maximize_the_topmost_element_after_k_moves;
 pub mod problem_2206_divide_array_into_equal_pairs;
+pub mod problem_2207_maximize_number_of_subsequences_in_a_string;
 pub mod problem_2208_minimum_operations_to_halve_array_sum;
 pub mod problem_2210_count_hills_and_valleys_in_an_array;
 pub mod problem_2215_find_the_difference_of_two_arrays;

src/problem_2207_maximize_number_of_subsequences_in_a_string/greedy.rs

@@ -0,0 +1,36 @@
+pub struct Solution;
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl Solution {
+    pub fn maximum_subsequence_count(text: String, pattern: String) -> i64 {
+        let [left, right]: [_; 2] = pattern.into_bytes().try_into().ok().unwrap();
+        let mut left_count = 0_u64;
+        let mut right_count = 0_u64;
+        let mut result = 0;
+
+        for c in text.into_bytes() {
+            result += left_count * u64::from(c == right);
+            left_count += u64::from(c == left);
+            right_count += u64::from(c == right);
+        }
+
+        (result + left_count.max(right_count)) as _
+    }
+}
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl super::Solution for Solution {
+    fn maximum_subsequence_count(text: String, pattern: String) -> i64 {
+        Self::maximum_subsequence_count(text, pattern)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_solution() {
+        super::super::tests::run::<super::Solution>();
+    }
+}

src/problem_2207_maximize_number_of_subsequences_in_a_string/mod.rs

@@ -0,0 +1,21 @@
+pub mod greedy;
+
+pub trait Solution {
+    fn maximum_subsequence_count(text: String, pattern: String) -> i64;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Solution;
+
+    pub fn run<S: Solution>() {
+        let test_cases = [(("abdcdbc", "ac"), 4), (("aabb", "ab"), 6)];
+
+        for ((text, pattern), expected) in test_cases {
+            assert_eq!(
+                S::maximum_subsequence_count(text.to_string(), pattern.to_string()),
+                expected,
+            );
+        }
+    }
+}