Add problem 2765: Longest Alternating Subarray

Author: EFanZh

src/lib.rs

@@ -1960,6 +1960,7 @@ pub mod problem_2740_find_the_value_of_the_partition;
 pub mod problem_2744_find_maximum_number_of_string_pairs;
 pub mod problem_2760_longest_even_odd_subarray_with_threshold;
 pub mod problem_2761_prime_pairs_with_target_sum;
+pub mod problem_2765_longest_alternating_subarray;
 
 #[cfg(test)]
 mod test_utilities;

src/problem_2765_longest_alternating_subarray/mod.rs

@@ -0,0 +1,18 @@
+pub mod sliding_window;
+
+pub trait Solution {
+    fn alternating_subarray(nums: Vec<i32>) -> i32;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Solution;
+
+    pub fn run<S: Solution>() {
+        let test_cases = [(&[2, 3, 4, 3, 4] as &[_], 4), (&[4, 5, 6], 2)];
+
+        for (nums, expected) in test_cases {
+            assert_eq!(S::alternating_subarray(nums.to_vec()), expected);
+        }
+    }
+}

src/problem_2765_longest_alternating_subarray/sliding_window.rs

@@ -0,0 +1,46 @@
+pub struct Solution;
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl Solution {
+    pub fn alternating_subarray(nums: Vec<i32>) -> i32 {
+        let mut expected_diff = 1;
+        let mut prev = -1;
+        let mut length = 0;
+        let mut result = 0_u32;
+
+        for num in nums {
+            let diff = num - prev;
+
+            if diff == expected_diff {
+                expected_diff = -expected_diff;
+                length += 1;
+            } else {
+                result = result.max(length);
+                (expected_diff, length) = if diff == 1 { (-1, 2) } else { (1, 1) };
+            }
+
+            prev = num;
+        }
+
+        result = result.max(length);
+
+        (if result < 2 { u32::MAX } else { result }) as _
+    }
+}
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl super::Solution for Solution {
+    fn alternating_subarray(nums: Vec<i32>) -> i32 {
+        Self::alternating_subarray(nums)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_solution() {
+        super::super::tests::run::<super::Solution>();
+    }
+}