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RemoveNthNodeFromEndOfList.java
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RemoveNthNodeFromEndOfList.java
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import java.util.Stack;
/**
* Given a linked list, remove the nth node from the end of list and return its head.
* <p>
* For example,
* <p>
* Given linked list: 1->2->3->4->5, and n = 2.
* <p>
* After removing the second node from the end, the linked list becomes 1->2->3->5.
* Note:
* Given n will always be valid.
* Try to do this in one pass.
* <p>
* Accepted.
*/
public class RemoveNthNodeFromEndOfList {
public ListNode removeNthFromEnd(ListNode head, int n) {
Stack<ListNode> stack = new Stack<>();
ListNode tmp = null, node = head;
for (; node != null; node = node.next) {
stack.push(node);
}
for (; n > 0 && !stack.empty(); n--) {
tmp = stack.pop();
}
if (tmp != null) {
if (!stack.empty()) {
stack.peek().next = tmp.next;
} else {
head = tmp.next;
}
}
return head;
}
public static class ListNode {
int val;
ListNode next;
ListNode(int x) {
val = x;
}
@Override
public boolean equals(Object obj) {
if (obj instanceof ListNode) {
ListNode node = (ListNode) obj;
return this.next == null && node.next == null || this.val == node.val && (this.next != null) && this.next.equals(node.next);
}
return false;
}
}
}