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

This commit is contained in:
Joe Ardent 2022-11-01 14:35:20 -07:00
parent 0ed2722260
commit a3bcf6b12c
2 changed files with 67 additions and 0 deletions

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[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]

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// 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));
}