Add problem 876: Middle of the Linked List

Author: EFanZh

src/lib.rs

@@ -718,6 +718,7 @@ pub mod problem_0870_advantage_shuffle;
 pub mod problem_0872_leaf_similar_trees;
 pub mod problem_0874_walking_robot_simulation;
 pub mod problem_0875_koko_eating_bananas;
+pub mod problem_0876_middle_of_the_linked_list;
 pub mod problem_1143_longest_common_subsequence;
 pub mod problem_1192_critical_connections_in_a_network;
 pub mod problem_1342_number_of_steps_to_reduce_a_number_to_zero;

src/problem_0876_middle_of_the_linked_list/iterative.rs

@@ -0,0 +1,37 @@
+use crate::data_structures::ListNode;
+
+pub struct Solution;
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+use std::iter;
+
+impl Solution {
+    pub fn middle_node(head: Option<Box<ListNode>>) -> Option<Box<ListNode>> {
+        let length = iter::successors(head.as_deref(), |node| node.next.as_deref()).count();
+        let dropped = length / 2;
+        let mut node = head;
+
+        for _ in 0..dropped {
+            node = node.unwrap().next;
+        }
+
+        node
+    }
+}
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl super::Solution for Solution {
+    fn middle_node(head: Option<Box<ListNode>>) -> Option<Box<ListNode>> {
+        Self::middle_node(head)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_solution() {
+        super::super::tests::run::<super::Solution>();
+    }
+}

src/problem_0876_middle_of_the_linked_list/mod.rs

@@ -0,0 +1,30 @@
+use crate::data_structures::ListNode;
+
+pub mod iterative;
+
+pub trait Solution {
+    fn middle_node(head: Option<Box<ListNode>>) -> Option<Box<ListNode>>;
+}
+
+#[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 &[_], &[3, 4, 5] as &[_]),
+            (&[1, 2, 3, 4, 5, 6], &[4, 5, 6]),
+        ];
+
+        for (head, expected) in test_cases {
+            assert_eq!(
+                test_utilities::iter_list(&S::middle_node(test_utilities::make_list(head.iter().copied())))
+                    .copied()
+                    .collect::<Box<_>>()
+                    .as_ref(),
+                expected
+            );
+        }
+    }
+}