remove nth node from end of list solution

Author: yhkee0404

remove-nth-node-from-end-of-list/yhkee0404.rs

@@ -0,0 +1,36 @@
+// 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 remove_nth_from_end(head: Option<Box<ListNode>>, n: i32) -> Option<Box<ListNode>> {
+        let mut dummy = Some(Box::new(ListNode::new(0)));
+        dummy.as_mut().unwrap().next = head;
+        Self::solve(&mut dummy, n);
+        dummy.unwrap().next
+    }
+    fn solve(head: &mut Option<Box<ListNode>>, n: i32) -> i32 {
+        match head {
+            None => 0,
+            Some(u) => {
+                let ans = Self::solve(&mut u.next, n) + 1;
+                if ans == n + 1 {
+                    u.next = u.next.as_mut().unwrap().next.take();
+                }
+                ans
+            }
+        }
+    }
+}