剑指offer 36.时间空间效率的平衡 两个链表的第一个公共结点

public class FindFirstCommonNode {
    public ListNode FindFirstCommonNode(ListNode pHead1, ListNode pHead2) {
        if (pHead1==null&&pHead2==null) {
            return null;
        }
        Stack<ListNode> stack1=new Stack<ListNode>();
        Stack<ListNode> stack2=new Stack<ListNode>();
        ListNode resultNode=null;
        while (pHead1!=null) {
            stack1.push(pHead1);
            pHead1=pHead1.next;
        }
        while (pHead2!=null) {
            stack2.push(pHead2);
            pHead2=pHead2.next;        
        }
        while (!stack1.isEmpty()&&!stack2.isEmpty()&&stack1.peek()==stack2.peek()) {
            stack2.pop();
            resultNode=stack1.pop();
        }
        return resultNode;
    }
    
    
    class ListNode {
        int val;
        ListNode next = null;

        ListNode(int val) {
            this.val = val;
        }
    }    
}