2074. Reverse Nodes in Even Length Groups: RETRY

Author: tan-wei

src/solution/mod.rs

@@ -1564,3 +1564,4 @@ mod s2069_walking_robot_simulation_ii;
 mod s2070_most_beautiful_item_for_each_query;
 mod s2071_maximum_number_of_tasks_you_can_assign;
 mod s2073_time_needed_to_buy_tickets;
+mod s2074_reverse_nodes_in_even_length_groups;

src/solution/s2074_reverse_nodes_in_even_length_groups.rs

@@ -0,0 +1,114 @@
+/**
+ * [2074] Reverse Nodes in Even Length Groups
+ *
+ * You are given the head of a linked list.
+ * The nodes in the linked list are sequentially assigned to non-empty groups whose lengths form the sequence of the natural numbers (1, 2, 3, 4, ...). The length of a group is the number of nodes assigned to it. In other words,
+ *
+ * 	The 1^st node is assigned to the first group.
+ * 	The 2^nd and the 3^rd nodes are assigned to the second group.
+ * 	The 4^th, 5^th, and 6^th nodes are assigned to the third group, and so on.
+ *
+ * Note that the length of the last group may be less than or equal to 1 + the length of the second to last group.
+ * Reverse the nodes in each group with an even length, and return the head of the modified linked list.
+ *  
+ * Example 1:
+ * <img alt="" src="https://assets.leetcode.com/uploads/2021/10/25/eg1.png" style="width: 699px; height: 124px;" />
+ * Input: head = [5,2,6,3,9,1,7,3,8,4]
+ * Output: [5,6,2,3,9,1,4,8,3,7]
+ * Explanation:
+ * - The length of the first group is 1, which is odd, hence no reversal occurs.
+ * - The length of the second group is 2, which is even, hence the nodes are reversed.
+ * - The length of the third group is 3, which is odd, hence no reversal occurs.
+ * - The length of the last group is 4, which is even, hence the nodes are reversed.
+ *
+ * Example 2:
+ * <img alt="" src="https://assets.leetcode.com/uploads/2021/10/25/eg2.png" style="width: 284px; height: 114px;" />
+ * Input: head = [1,1,0,6]
+ * Output: [1,0,1,6]
+ * Explanation:
+ * - The length of the first group is 1. No reversal occurs.
+ * - The length of the second group is 2. The nodes are reversed.
+ * - The length of the last group is 1. No reversal occurs.
+ *
+ * Example 3:
+ * <img alt="" src="https://assets.leetcode.com/uploads/2021/11/17/ex3.png" style="width: 348px; height: 114px;" />
+ * Input: head = [1,1,0,6,5]
+ * Output: [1,0,1,5,6]
+ * Explanation:
+ * - The length of the first group is 1. No reversal occurs.
+ * - The length of the second group is 2. The nodes are reversed.
+ * - The length of the last group is 2. The nodes are reversed.
+ *
+ *  
+ * Constraints:
+ *
+ * 	The number of nodes in the list is in the range [1, 10^5].
+ * 	0 <= Node.val <= 10^5
+ *
+ */
+pub struct Solution {}
+use crate::util::linked_list::{to_list, ListNode};
+
+// problem: https://leetcode.com/problems/reverse-nodes-in-even-length-groups/
+// discuss: https://leetcode.com/problems/reverse-nodes-in-even-length-groups/discuss/?currentPage=1&orderBy=most_votes&query=
+
+// submission codes start here
+
+// Definition for singly-linked list.
+// #[derive(PartialEq, Eq, Clone, Debug)]
+// pub struct ListNode {
+//   pub val: i32,
+//   pub next: Option<Box<ListNode>>
+// }
+//
+// impl ListNode {
+//   #[inline]
+//   fn new(val: i32) -> Self {
+//     ListNode {
+//       next: None,
+//       val
+//     }
+//   }
+// }
+impl Solution {
+    pub fn reverse_even_length_groups(head: Option<Box<ListNode>>) -> Option<Box<ListNode>> {
+        Some(Box::new(ListNode::new(0)))
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    #[ignore]
+    fn test_2074_example_1() {
+        let head = linked![5, 2, 6, 3, 9, 1, 7, 3, 8, 4];
+
+        let result = linked![5, 6, 2, 3, 9, 1, 4, 8, 3, 7];
+
+        assert_eq!(Solution::reverse_even_length_groups(head), result);
+    }
+
+    #[test]
+    #[ignore]
+    fn test_2074_example_2() {
+        let head = linked![1, 1, 0, 6];
+
+        let result = linked![1, 0, 1, 6];
+
+        assert_eq!(Solution::reverse_even_length_groups(head), result);
+    }
+
+    #[test]
+    #[ignore]
+    fn test_2074_example_3() {
+        let head = linked![1, 1, 0, 6, 5];
+
+        let result = linked![1, 0, 1, 5, 6];
+
+        assert_eq!(Solution::reverse_even_length_groups(head), result);
+    }
+}