链表问题——两个单链表生成相加链表

ゞ浴缸里的玫瑰 2022-06-03 04:46 136阅读 0赞

【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;
        }
    
    }