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[leetcode]add two numbers

admin 11月 11, 2020 0

题目描述

You are given two linked lists representing two non-negative numbers. 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.

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

代码


 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class  {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode dummy = new ListNode(0);
        
        ListNode p = l1, q = l2, curr = dummy;
        
        int carry = 0;
        //可以用||把为空的一方的加数置为0就可以
        //用&&也可以，后面再将不空链接到尾部就行了
        while(p != null || q != null){
            int x = p != null ? p.val : 0;
            int y = q != null ? q.val : 0;
            
            int sum = x + y + carry;
            carry = sum / 10;

            curr.next = new ListNode(sum % 10);
            curr = curr.next;
            
            if(p != null) p = p.next;
            if(q != null) q = q.next;
        }
        
        if(carry > 0){
            curr.next = new ListNode(carry);
        }
        
        return dummy.next;
    }
}