slightly wasteful solution for remove-nth-from-back-of-linked-list

remove_nth_from_list_end/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "remove_nth_from_list_end"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

remove_nth_from_list_end/src/main.rs

@@ -0,0 +1,59 @@
+// Definition for singly-linked list.
+#[derive(PartialEq, Eq, Clone, Debug)]
+pub struct ListNode {
+    pub val: i32,
+    pub next: Option<Box<ListNode>>,
+}
+
+struct Solution();
+
+impl Solution {
+    pub fn remove_nth_from_end(head: Option<Box<ListNode>>, n: i32) -> Option<Box<ListNode>> {
+        let stack = Solution::unmake(head);
+        let ded = stack.len() - n as usize;
+        let stack: Vec<i32> = stack
+            .into_iter()
+            .enumerate()
+            .filter_map(|e| if e.0 != ded { Some(e.1) } else { None })
+            .collect();
+
+        Solution::make(&stack)
+    }
+
+    pub fn make(list: &[i32]) -> Option<Box<ListNode>> {
+        let mut head = None;
+        for &val in list.iter().rev() {
+            let tail = head.clone();
+            let node = Box::new(ListNode { val, next: tail });
+            head = Some(node);
+        }
+        head
+    }
+
+    pub fn unmake(mut list: Option<Box<ListNode>>) -> Vec<i32> {
+        let mut v = Vec::with_capacity(30);
+        while let Some(node) = list {
+            v.push(node.val);
+            list = node.next;
+        }
+        v
+    }
+}
+
+fn print(mut list: Option<Box<ListNode>>) {
+    print!("[");
+    while let Some(node) = list {
+        print!("{} ", node.val);
+        list = node.next;
+    }
+    println!("]");
+}
+
+fn main() {
+    print(Solution::remove_nth_from_end(
+        Solution::make(&[1, 2, 3, 4, 5]),
+        2,
+    ));
+
+    print(Solution::remove_nth_from_end(Solution::make(&[1]), 1));
+}