链表翻转

单链表

  /**
     * 单链表
     */
    public static class Linked {
        private String value;
        private Linked next;

        public Linked(String value) {
            this.value = value;
        }

        public String getValue() {
            return value;
        }

        public void setValue(String value) {
            this.value = value;
        }

        public Linked getNext() {
            return next;
        }

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

递归实现

    /**
     * 链表翻转，递归实现
     *
     * @param head head
     * @return
     */
    public Linked flipByRecursion(Linked head) {
        if (head == null || head.next == null) return head;

        Linked tailLinked = flipByRecursion(head.next);

        head.next.setNext(head);
        head.setNext(null);

        return tailLinked;
    }

循环实现

  /**
     * 循环实现
     *
     * @param head head
     * @return
     */
    public Linked flipByLoop(Linked head) {
        if (head == null || head.next == null) return head;

        Linked next = null;
        Linked pre = null;

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

        return pre;
    }