Implemented p19
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1 changed files with 24 additions and 2 deletions
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@ -1,9 +1,26 @@
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use super::linked_list::ListNode;
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struct Solution;
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pub struct Solution;
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impl Solution {
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pub fn remove_nth_from_end(head: Option<Box<ListNode>>, n: i32) -> Option<Box<ListNode>> {
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return None;
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let mut head = head.unwrap();
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let mut node_before_nth: &mut Box<ListNode>;
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// unsafe is required to have immutable and mutable references at the same time
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// in order to avoid cloning the list altogether
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unsafe { node_before_nth = &mut *(&mut head as *mut Box<ListNode>); };
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let mut tail = &head;
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for _ in 0..n-1 {
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tail = tail.next.as_ref().unwrap();
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}
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if tail.next.is_none() { return head.next; }
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else { tail = tail.next.as_ref().unwrap(); }
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while tail.next.is_some() {
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tail = tail.next.as_ref().unwrap();
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node_before_nth = node_before_nth.next.as_mut().unwrap();
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}
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let node_to_remove = node_before_nth.next.as_mut().unwrap();
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node_before_nth.next = node_to_remove.next.take();
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return Some(head);
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}
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}
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@ -21,3 +38,8 @@ fn test2() {
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fn test3() {
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assert_eq!(Solution::remove_nth_from_end(list![1,2], 1), list![1]);
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}
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#[test]
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fn test4() {
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assert_eq!(Solution::remove_nth_from_end(list![1,2], 2), list![2]);
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}
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