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Leetcode-2. Add Two Numbers

2017.02.25 尤淇  热度 ℃

题目

You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.

You may assume the two numbers do not contain any leading zero, except the number 0 itself.

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8

代码

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public ListNode addTwoNumbers(ListNode l1, ListNode l2) {

        boolean flag = false;

        int v = l1.val + l2.val;

        if(v > 9) {
            //需要进位
            flag = true;
        }
        ListNode head = new ListNode(v % 10);
        ListNode n = head;


        ListNode n1 = l1.next;
        ListNode n2 = l2.next;

        while(n1 != null || n2 != null || flag){
            if(n1 == null){
                n1 = new ListNode(0);
            }
            if(n2 == null){
                n2 = new ListNode(0);
            }

            v = n1.val + n2.val;
            if(flag){
                v +=1;
                flag = false;
            }

            if(v > 9) {
                //需要进位
                flag = true;
            }
            n.next = new ListNode(v % 10);
            n = n.next;

            n1 = n1.next;
            n2 = n2.next;
        }

        return head;
    }

数据结构

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public class ListNode {
    public int val;
    public ListNode next;

    public ListNode(int x) {
        val = x;
    }
}

总结

  • 多写几个例子研究规律；
  • 其实规律就是两个链接顺序节点做加法，进位向后一位进位；