链表问题——两个单链表生成相加链表

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【题目】
　　假设链表中每一个节点的值都在0-9之间，那么链表整体就可以代表一个整数
　　例如：9->3->7代表937
　　给定两个这种链表的头节点head1和head2，请生成代表两个整数相加值的结果链表，并返回结果链表的头节点，注意进位问题

【代码】

//介绍两种方法，一种利用栈，一种利用逆序链表
import java.util.*;

class Node
{
    public int value;
    public Node next;

    public Node(int data)
    {
        this.value = data;
    }
}

class test{
    //利用栈
    public Node addLists1(Node head1,Node head2)
    {
        Stack<Integer> s1 = new Stack<Integer>();
        Stack<Integer> s2 = new Stack<Integer>();
        while(head1!=null)
        {
            s1.push(head1.value);
            head1 = head1.next;
        }
        while(head2!=null)
        {
            s2.push(head2.value);
            head2 = head2.next;
        }

        int ca = 0;  //进位
        int n1 = 0;
        int n2 = 0;
        int n = 0;
        Node node = null;
        Node pre = null;

        while(!s1.isEmpty() || !s2.isEmpty())
        {
            n1 = s1.isEmpty() ? 0 : s1.pop();
            n2 = s2.isEmpty() ? 0 : s2.pop();
            pre = node;
            node = new Node(n%10);
            node.next = pre;
            ca = n/10;
        }
        if(ca==1)
        {
            pre = node;
            node = new Node(1);
            node.next = pre;
        }
        return node;
    }

    //利用链表逆序
    public Node addList2(Node head1,Node head2)
    {
        head1 = reverseList(head1);
        head2 = reverseList(head2);
        int ca = 0;  //进位
        int n1 = 0;
        int n2 = 0;
        int n = 0;
        Node c1 = head1;
        Node c2 = head2;
        Node node = null;
        Node pre = null;
        while(c1!=null || c2!=null)
        {
            n1 = c1 != null ? c1.value : 0;
            n2 = c2 != null ? c2.value : 0;
            n = n1 + n2 + ca;
            pre = node;
            node = new Node(n%10);
            node.next = pre;
            ca = n/10;
            c1 = c1 != null ? c1.next : null;
            c2 = c2 != null ? c2.next : null;
        }

        if(ca==1)
        {
            pre = node;
            node = new Node(1);
            node.next = pre;
        }

        reverseList(head1);
        reverseList(head2);

        return node;
    }

    public Node reverseList(Node head)
    {
        Node pre = null;
        Node next = null;
        while(head!=null)
        {
            next = head.next;
            head.next = pre;
            pre = head;
            head = next;
        }
        return pre;
    }

}