Add two Numbers

Add Two Numbers

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

比较简单，还是用Java编写，一次过O(∩_∩)O

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        int s = l1.val+l2.val,carry = 0;
        if(s>9)
        {
            s=s-10;
            carry=1;
        }
        ListNode sum = new ListNode(s);
        ListNode next= sum;
        while(l1.next!=null&&l2.next!=null)
        {
            s=l1.next.val+l2.next.val+carry;
            carry=0;
            if(s>9)
            {
                s=s-10;
                carry=1;
            }
            next.next=new ListNode(s);
            next=next.next;
            l1=l1.next;
            l2=l2.next;
        }
        while(l1.next==null&&l2.next!=null)
        {
            s=l2.next.val+carry;
            carry=0;
            if(s>9)
            {
                s=s-10;
                carry=1;
            }
            next.next=new ListNode(s);
            next=next.next;
            l2=l2.next;
        }
        while(l1.next!=null&&l2.next==null)
        {
            s=l1.next.val+carry;
            carry=0;
            if(s>9)
            {
                s=s-10;
                carry=1;
            }
            next.next=new ListNode(s);
            next=next.next;
            l1=l1.next;
        }
        if(carry==1)
            next.next=new ListNode(carry);
        
        return sum;
    }
}

运行时间排最后。。因为最近在学Java。查了一下其他解决办法。下面那个是445ms的，比我的快了1ms，虽然时间差不多，不过看着就比我那个好多了。╮(╯▽╰)╭

public class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
       int carry =0;
 
        ListNode newHead = new ListNode(0);
        ListNode p1 = l1, p2 = l2, p3=newHead;
 
        while(p1 != null || p2 != null){
            if(p1 != null){
                carry += p1.val;
                p1 = p1.next;
            }
 
            if(p2 != null){
                carry += p2.val;
                p2 = p2.next;
            }
 
            p3.next = new ListNode(carry%10);
            p3 = p3.next;
            carry /= 10;
        }
 
        if(carry==1) 
            p3.next=new ListNode(1);
 
        return newHead.next;
    }
}

参考来源：http://www.programcreek.com/2012/12/add-two-numbers/