19.Remove Nth Node From End of List

好吧，參考的答案…感覺這種思路棒棒的…and以後要用java…

public class Solution {
    public ListNode removeNthFromEnd(ListNode head, int n) {
        if(head==null) return null;

        //定義兩個指針，第一個保持指向最初的head指針
        //使head指針移動，先到達訪問第n個結點，第二個指針開始出發
        //則當head訪問完末尾結點時，第二個正好到達從後往前數的第n個結點
        ListNode dummy = new ListNode(0);
        dummy.next = head;
        ListNode follower = dummy;

        for(int i=0;i<n;i++){
            if(head==null) return null;
            head = head.next;
        }

        while(head!=null){
            head = head.next;
            follower = follower.next;
        }

        follower.next = follower.next.next;

        return dummy.next;
    }
}