Add problem 3201: Find the Maximum Length of Valid Subsequence I

Author: EFanZh

src/lib.rs

@@ -2134,6 +2134,7 @@ pub mod problem_3194_minimum_average_of_smallest_and_largest_elements;
 pub mod problem_3195_find_the_minimum_area_to_cover_all_ones_i;
 pub mod problem_3196_maximize_total_cost_of_alternating_subarrays;
 pub mod problem_3200_maximum_height_of_a_triangle;
+pub mod problem_3201_find_the_maximum_length_of_valid_subsequence_i;
 pub mod problem_3350_adjacent_increasing_subarrays_detection_ii;
 
 #[cfg(test)]

src/problem_3201_find_the_maximum_length_of_valid_subsequence_i/dynamic_programming.rs

@@ -0,0 +1,38 @@
+pub struct Solution;
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl Solution {
+    pub fn maximum_length(nums: Vec<i32>) -> i32 {
+        let mut max_even = 0;
+        let mut max_odd = 0;
+        let mut max_alt_even = 0;
+        let mut max_alt_odd = 0;
+
+        for num in nums {
+            (max_even, max_odd, max_alt_even, max_alt_odd) = if num & 1 == 0 {
+                (max_even + 1, max_odd, max_alt_even.max(max_alt_odd + 1), max_alt_odd)
+            } else {
+                (max_even, max_odd + 1, max_alt_even, max_alt_odd.max(max_alt_even + 1))
+            }
+        }
+
+        max_even.max(max_odd).max(max_alt_even).max(max_alt_odd)
+    }
+}
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl super::Solution for Solution {
+    fn maximum_length(nums: Vec<i32>) -> i32 {
+        Self::maximum_length(nums)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_solution() {
+        super::super::tests::run::<super::Solution>();
+    }
+}

src/problem_3201_find_the_maximum_length_of_valid_subsequence_i/mod.rs

@@ -0,0 +1,23 @@
+pub mod dynamic_programming;
+
+pub trait Solution {
+    fn maximum_length(nums: Vec<i32>) -> i32;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Solution;
+
+    pub fn run<S: Solution>() {
+        let test_cases = [
+            (&[1, 2, 3, 4] as &[_], 4),
+            (&[1, 2, 1, 1, 2, 1, 2], 6),
+            (&[1, 3], 2),
+            (&[2, 7, 7, 7, 8], 3),
+        ];
+
+        for (nums, expected) in test_cases {
+            assert_eq!(S::maximum_length(nums.to_vec()), expected);
+        }
+    }
+}