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通过一次遍历找到倒数节点

// 通过一次遍历找到倒数节点
public class HeadToEnd {

    private HeadToEnd() {

    }

    public static final HeadToEnd create() {
        return new HeadToEnd();
    }

    public Node nthNodeFromEnd(Node head, int nth) {
        if (null == head) {
            throw new NullPointerException();
        }
        if (null == head.getNext()) {
            throw new IllegalArgumentException();
        }
        Node temp = head;
        Node find = null;
        for (int i = 1; i < nth; i++) {
            if (null == temp) {
                break;
            } else {
                temp = temp.getNext();
            }
        }
        for (; null != temp; ) {
            if (null == find) {
                find = head;
            } else {
                find = find.getNext();
            }
            temp = temp.getNext();
        }
        if (null != find) {
            return find;
        } else {
            // 答印警告
            return null;
        }
    }

    public static final void main(String[] args) {
        CreateList create = CreateList.create();
        Node head = create.buildNormal(8);
        Node temp = head;
        for (; null != temp; ) {
            System.out.println(temp);
            temp = temp.getNext();
        }
        HeadToEnd find = HeadToEnd.create();
        Node nth = find.nthNodeFromEnd(head, 13);
        System.out.println(nth);
    }

}

辅助类1：节点

public class Node {

    private Node next;
    private int date;

    private Node() {

    }

    public static final Node create() {
        return new Node();
    }

    public void setNext(final Node next) {
        this.next = next;
    }

    public Node getNext() {
        return next;
    }

    public int getDate() {
        return date;
    }

    public void setDate(int date) {
        this.date = date;
    }

    @Override
    public String toString() {
        return "Node{" +
                "date=" + date +
                '}';
    }
}

辅助类2：链表创建类

public class CreateList {

    private CreateList() {

    }

    public static final CreateList create() {
        return new CreateList();
    }

    public final Node buildNormal(int length) {
        return build(length).getHead();
    }

    private final HeadTail build(int length) {
        final Node head = Node.create();
        Node current = head;
        for (int i = 0; i < length; i++) {
            Node node = Node.create();
            node.setDate(i + 1);
            current.setNext(node);
            current = node;
        }
        final HeadTail ht = HeadTail.create(head, current);
        return ht;
    }

    public final Node buildLoop(int listLength, int loopLength) {
        if (listLength < 0) {
            throw new IllegalArgumentException();
        }
        if (listLength == 0) {
            return Node.create();
        }
        if (loopLength <= 0) {
            return buildNormal(listLength);
        }
        if (loopLength > listLength) {
            throw new IllegalArgumentException();
        }
        HeadTail ht = build(listLength);
        Node head = ht.getHead();
        Node tail = ht.getTail();
        if (loopLength == listLength) {
            tail.setNext(head.getNext());
        } else {
            Node temp = head;
            int dur = listLength - loopLength;
            for (int i = 0; i < dur; i++) {
                temp = temp.getNext();
            }
            tail.setNext(temp.getNext());
        }
        return head;
    }

    private static final class HeadTail {
        private final Node head;
        private final Node tail;

        private HeadTail(final Node head, final Node tail) {
            this.head = head;
            this.tail = tail;
        }

        public static final HeadTail create(final Node head, final Node tail) {
            return new HeadTail(head, tail);
        }

        public Node getHead() {
            return head;
        }

        public Node getTail() {
            return tail;
        }
    }

}

运行截图

image.png

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有问题欢迎指正，这是新鲜出炉的
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本文为原创文章，转载请注明出处，谢谢你……