Add problem 0896: Monotonic Array

src/lib.rs

@@ -449,6 +449,7 @@ pub mod problem_0884_uncommon_words_from_two_sentences;
 pub mod problem_0889_construct_binary_tree_from_preorder_and_postorder_traversal;
 pub mod problem_0890_find_and_replace_pattern;
 pub mod problem_0895_maximum_frequency_stack;
+pub mod problem_0896_monotonic_array;
 pub mod problem_0900_rle_iterator;
 pub mod problem_0915_partition_array_into_disjoint_intervals;
 pub mod problem_0916_word_subsets;

src/problem_0896_monotonic_array/iterative.rs

@@ -0,0 +1,33 @@
+pub struct Solution;
+
+impl Solution {
+    pub fn is_monotonic(nums: Vec<i32>) -> bool {
+        let mut prev = nums[0];
+        let mut increasing = None;
+        for &num in &nums[1..] {
+            match (num.cmp(&prev), increasing) {
+                (std::cmp::Ordering::Less, None) => increasing = Some(false),
+                (std::cmp::Ordering::Greater, None) => increasing = Some(true),
+                (std::cmp::Ordering::Less, Some(true))
+                | (std::cmp::Ordering::Greater, Some(false)) => return false,
+                _ => (),
+            };
+            prev = num;
+        }
+        true
+    }
+}
+
+impl super::Solution for Solution {
+    fn is_monotonic(nums: Vec<i32>) -> bool {
+        Self::is_monotonic(nums)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_solution() {
+        super::super::tests::run::<super::Solution>();
+    }
+}

src/problem_0896_monotonic_array/mod.rs

@@ -0,0 +1,24 @@
+pub mod iterative;
+
+pub trait Solution {
+    fn is_monotonic(nums: Vec<i32>) -> bool;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Solution;
+
+    pub fn run<S: Solution>() {
+        let test_cases = [
+            (&[1, 2, 2, 3] as &[_], true),
+            (&[6, 5, 4, 4], true),
+            (&[1, 3, 2], false),
+            (&[5, 3, 2, 4, 1], false),
+            (&[1, 1, 1], true),
+        ];
+
+        for (nums, expected) in test_cases {
+            assert_eq!(S::is_monotonic(nums.to_vec()), expected);
+        }
+    }
+}