本地构建LeetCode链表相关测试用例

ListNode

public class ListNode {
    public int val;
    public ListNode next;
    public ListNode() {}
    public ListNode(int val) { this.val = val; }
    public ListNode(int val, ListNode next) { this.val = val; this.next = next; }
}

尾插法构建带头节点的单链表

    /**
     * 尾插法构建带头节点的单链表
     * @param head
     * @param nums
     * @return
     */
    public ListNode creatListByArray(ListNode head, int[] nums) {
        ListNode p = head;
        for (int i = 0; i < nums.length; i++) {
            ListNode q = new ListNode();
            p.next = q;
            p.next.val = nums[i];
            p = p.next;
        }
        return head;
    }

使链表变成环路

    /**
     * 使链表变成环路
     * pos来表示链表尾连接到链表中的位置
     * @param head
     * @param pos
     * @return
     */
    public ListNode createCycleList(ListNode head, int pos) {
        ListNode p = head;
        ListNode q = new ListNode();
        if (pos == 0 && p.next == null) {
            p.next = head;
        } else {
            int index = 0;
            while (p.next != null) {
                if (index == pos) {
                    q = p;
                }
                p = p.next;
                index++;
            }
            if (pos <= index) {
                p.next = q;
            }
        }
        return head;
    }

使两个链表相交

    /**
     * 使两个链表相交
     * 在java中除去基本数据类型，其他都是引用数据类型，自己定义的类也是
     * @param headA
     * @param headB
     * @param skipA
     * @param skipB
     */
    public void createIntersectionList(ListNode headA, ListNode headB, int skipA, int skipB) {
        ListNode p = headA;
        ListNode q = headB;
        while (p != null && skipA > 1) {
            p = p.next;
            skipA--;
        }
        while (q != null && skipB > 1) {
            q = q.next;
            skipB--;
        }
        q.next = p.next; // 类、接口、数组都是引用类型
    }

根据val查询结点

    /**
     * 根据val查询结点
     * @param head
     * @param val
     * @return
     */
    public ListNode findNodeByVal(ListNode head, int val) {
        ListNode p = head;
        while (p != null) {
            if (p.val == val) {
                return p;
            }
            p = p.next;
        }
        return null;
    }

打印带头结点的链表

    /**
     * 打印带头结点的链表
     * @param head
     */
    public void showList(ListNode head) {
        if (head == null) {
            System.out.println();
            return;
        }
        ListNode p = head.next;
        while (p != null) {
            System.out.print(p.val + " ");
            p = p.next;
        }
        System.out.println();
    }

打印不带头结点的链表

    /**
     * 打印不带头结点的链表
     * @param head
     */
    public void showNoHeadList(ListNode head) {
        if (head == null) {
            System.out.println();
            return;
        }
        ListNode p = head;
        while (p != null) {
            System.out.print(p.val + " ");
            p = p.next;
        }
        System.out.println();
    }

打印结点

    /**
     * 打印结点
     * @param node
     */
    public void showNode(ListNode node) {
        if (node == null) {
            System.out.println();
        } else {
            System.out.println(node.val);
        }
    }