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| 1 | +#[cfg(feature = "serde")] |
| 2 | +use serde::{Deserialize, Serialize}; |
| 3 | +/// ## Description |
| 4 | +/// |
| 5 | +/// The struct works by having a value and an optional pointer to a next ListNode. |
| 6 | +/// When writing the nodes you need to start from the last one and make your way down to the first |
| 7 | +/// one. |
| 8 | +/// |
| 9 | +/// The struct signature is entirely 1:1 with LeetCode with additional optional features like |
| 10 | +/// serde. |
| 11 | +/// |
| 12 | +/// ## Example |
| 13 | +/// |
| 14 | +/// ```rust |
| 15 | +/// use leetcode_trees_rs::utils::ListNode; |
| 16 | +/// use std::boxed::Box; |
| 17 | +/// use std::option::Option; |
| 18 | +/// |
| 19 | +/// // Last node |
| 20 | +/// let node_3 = ListNode::new(7); |
| 21 | +/// |
| 22 | +/// // Second node |
| 23 | +/// let node_2 = ListNode{ |
| 24 | +/// val: 6, |
| 25 | +/// next: Some(Box::new(node_3)), |
| 26 | +/// }; |
| 27 | +/// |
| 28 | +/// // First node |
| 29 | +/// let node_1 = ListNode { |
| 30 | +/// val: 5, |
| 31 | +/// next: Some(Box::new(node_2)), |
| 32 | +/// }; |
| 33 | +/// ``` |
| 34 | +/// Result: 5 -> 6 -> 7 -> `None` |
| 35 | +/// |
| 36 | +/// ## Big O |
| 37 | +/// |
| 38 | +/// Peeking/modifying the first element -> O(1) |
| 39 | +/// Peeking/modifying the last element -> O(n) |
| 40 | +/// Removing the first element -> O(1) |
| 41 | +/// Removing any next element -> O(n) |
| 42 | +/// Adding a new element at the end -> O(n) |
| 43 | +/// Adding a new element at the start -> O(1) |
| 44 | +/// Searching -> O(n) |
| 45 | +#[derive(PartialEq, Eq, Clone, Debug)] |
| 46 | +#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))] |
| 47 | +pub struct ListNode { |
| 48 | + /// This uses normal i32 values that can be serialized and deserialized using serde if wanted. |
| 49 | + pub val: i32, |
| 50 | + |
| 51 | + /// An optional box for a next ListNode. |
| 52 | + #[cfg_attr(feature = "serde", serde(skip))] |
| 53 | + pub next: Option<Box<ListNode>>, |
| 54 | +} |
| 55 | + |
| 56 | +impl ListNode { |
| 57 | + /// Used to make a new ListNode with next as `None`. |
| 58 | + #[inline] |
| 59 | + pub fn new(val: i32) -> Self { |
| 60 | + ListNode { next: None, val } |
| 61 | + } |
| 62 | +} |
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