57 lines
1.3 KiB
Rust
57 lines
1.3 KiB
Rust
#[derive(PartialEq, Eq, Clone, Debug)]
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pub struct ListNode {
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pub val: i32,
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pub next: Option<Box<ListNode>>,
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}
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impl ListNode {
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#[inline]
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fn new(val: i32) -> Self {
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ListNode { next: None, val }
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}
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}
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pub struct Solution;
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impl Solution {
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pub fn reverse_list(head: Option<Box<ListNode>>) -> Option<Box<ListNode>> {
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let mut arr: Vec<i32> = vec![];
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let mut current_node = head;
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while let Some(node) = current_node.take() {
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arr.push(node.val);
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current_node = node.next;
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}
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if arr.is_empty() {
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return None;
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}
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let mut head = Some(Box::new(ListNode::new(*arr.last().unwrap())));
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let mut current_node = &mut head;
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for &num in arr[..arr.len() - 1].iter().rev() {
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current_node.as_mut().unwrap().next = Some(Box::new(ListNode::new(num)));
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current_node = &mut current_node.as_mut().unwrap().next;
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}
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head
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}
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pub fn reverse_list_2(mut head: Option<Box<ListNode>>) -> Option<Box<ListNode>> {
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if head.is_none() {
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return None;
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}
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let mut p: Option<Box<ListNode>> = None;
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while let Some(mut node) = head.take() {
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let next = node.next;
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node.next = p;
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p = Some(node);
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head = next;
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}
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p
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}
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}
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