初级算法（2）-链表

public static void deleteNode(ListNode node) {
        if(node == null || node.next == null){
            return;
        }
        ListNode next = node.next;
        node.val = next.val;
        node.next = next.next;
    }

if(head == null || head.next == null) {
            return head;
        }
        // 新的节点
        ListNode pre = null;
        ListNode next = null;
        while (head != null) {
            // 首先保存待移动节点的下一个节点
            next = head.next;
            // 分离当前节点，并指向新的节点
            head.next = pre;
            // 挪动新节点的指针
            pre = head;
            // 挪动旧节点指针
            head = next;
        }
        return pre;

if(l1 == null || l2 ==null) {
            return l1 == null ? l2 : l1;
        }
        ListNode head = l1.val < l2.val ? l1 : l2;
        ListNode cur1 = head == l1 ? l1 : l2;
        ListNode cur2 = head == l1 ? l2 : l1;
        ListNode pre = null ;
        ListNode next = null;
        while(!(cur1 == null || cur2 == null)) {
            // 值比另外一个节点小，就直接遍历下一个节点
            if (cur1.val <= cur2.val) {
                pre = cur1;
                cur1 = cur1.next;
            } else {
                // 将cur2的节点插入到cur1中
                next = cur2.next;
                pre.next = cur2;
                cur2.next = cur1;
                pre = cur2;
                cur2 = next;
            }
        }
        pre.next = cur1 == null ? cur2 : cur1;
        return head;

if (head == null || head.next == null || head.next.next == null) {
            return false;
        }
        ListNode step1 = head;
        ListNode step2 = head;
        while (step2 != null && step2.next !=null) {
            step1 = step1.next;
            step2 = step2.next.next;
            if (step1 == step2) {
                return true;
            }
        }
        return false;