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class Solution {
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  public ListNode removeNthFromEnd(ListNode head, int n) {
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    ListNode temp = head;
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    int len = 0;
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    if (head == null || head.next == null) return null;
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    while (temp != null) {
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      temp = temp.next;
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      len++;
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    }
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    if (len == n) return head.next;
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    int frontlen = len - n - 1;
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    ListNode first = head.next;
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    ListNode second = head;
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    int count = 0;
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    while (first != null) {
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      if (count == frontlen) {
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        second.next = first.next;
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        break;
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      } else {
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        first = first.next;
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        second = second.next;
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        count++;
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      }
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    }
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    return head;
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  }
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}