feat(linked-list): 206_reverse_linked_list.rs

Author: whisperpine

README.md

@@ -124,3 +124,9 @@ so that you can use `just tf TEST` command to test.
 | - | - | - |
 | 121. Best Time to Buy and Sell Stock | Easy | [121_best_time_to_buy_and_sell_stock.rs](./tests/121_best_time_to_buy_and_sell_stock.rs) |
 | 3. Longest Substring Without Repeating Characters | Medium | [3_longest_substring_without_repeating_characters.rs](./tests/3_longest_substring_without_repeating_characters.rs) |
+
+### Linked List
+
+| Problem | Difficulty | Solution |
+| - | - | - |
+| 206. Reverse Linked List | Easy | [206_reverse_linked_list.rs](./tests/206_reverse_linked_list.rs) |

tests/206_reverse_linked_list.rs

@@ -0,0 +1,43 @@
+// 206. Reverse Linked List
+// https://leetcode.com/problems/reverse-linked-list/description/
+// Topics: Linked List.
+// Difficulty: Easy.
+
+#[test]
+fn test_206_reverse_linked_list() {}
+
+#[derive(Debug)]
+pub struct Solution;
+
+// ---------------------------------
+// copy to leetcode starts from 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_list(head: Option<Box<ListNode>>) -> Option<Box<ListNode>> {
+        let mut prev: Option<Box<ListNode>> = None;
+        let mut curr: Option<Box<ListNode>> = head;
+
+        while let Some(mut boxed_node) = curr {
+            curr = boxed_node.next;
+            boxed_node.next = prev;
+            prev = Some(boxed_node);
+        }
+
+        prev
+    }
+}