Add problem 1968: Array With Elements Not Equal to Average of Neighbors

src/lib.rs

@@ -1363,6 +1363,7 @@ pub mod problem_1957_delete_characters_to_make_fancy_string;
 pub mod problem_1961_check_if_string_is_a_prefix_of_array;
 pub mod problem_1962_remove_stones_to_minimize_the_total;
 pub mod problem_1967_number_of_strings_that_appear_as_substrings_in_word;
+pub mod problem_1968_array_with_elements_not_equal_to_average_of_neighbors;
 
 #[cfg(test)]
 mod test_utilities;

src/problem_1968_array_with_elements_not_equal_to_average_of_neighbors/iterative.rs

@@ -0,0 +1,42 @@
+pub struct Solution;
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+use std::mem;
+
+impl Solution {
+    pub fn rearrange_array(nums: Vec<i32>) -> Vec<i32> {
+        let mut nums = nums;
+        let mut iter = nums.iter_mut();
+        let prev_1 = iter.next().unwrap();
+        let mut prev_2 = iter.next().unwrap();
+        let mut is_decreasing = prev_2 < prev_1;
+
+        for value in iter {
+            if is_decreasing == (value < prev_2) {
+                mem::swap(prev_2, value);
+            }
+
+            prev_2 = value;
+            is_decreasing = !is_decreasing;
+        }
+
+        nums
+    }
+}
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl super::Solution for Solution {
+    fn rearrange_array(nums: Vec<i32>) -> Vec<i32> {
+        Self::rearrange_array(nums)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_solution() {
+        super::super::tests::run::<super::Solution>();
+    }
+}

src/problem_1968_array_with_elements_not_equal_to_average_of_neighbors/mod.rs

@@ -0,0 +1,34 @@
+pub mod iterative;
+
+pub trait Solution {
+    fn rearrange_array(nums: Vec<i32>) -> Vec<i32>;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Solution;
+    use crate::test_utilities;
+
+    pub fn run<S: Solution>() {
+        let test_cases = [&[1, 2, 3, 4, 5] as &[_], &[6, 2, 0, 9, 7]];
+
+        for nums in test_cases {
+            let result = S::rearrange_array(nums.to_vec());
+
+            assert_eq!(
+                test_utilities::unstable_sorted(result.iter().copied()),
+                test_utilities::unstable_sorted(nums.iter().copied()),
+            );
+
+            let mut prev_1 = i32::MIN;
+            let mut prev_2 = i32::MIN;
+
+            for value in result {
+                assert_ne!(prev_1 + value, prev_2 << 1);
+
+                prev_1 = prev_2;
+                prev_2 = value;
+            }
+        }
+    }
+}