Add two numbers@leetcode

刷题必备书籍：Cracking the Coding Interview: 150 Programming Questions and Solutions 

简历：The Google Resume: How to Prepare for a Career and Land a Job at Apple, Microsoft, Google, or any Top Tech Company
算法学习书籍：Introduction to Algorithms
编程珠玑：Programming Pearls (2nd Edition)
C++ 学习：The C++ Programming Language, 4th Edition
经典操作系统书籍，龙书：Operating System Concepts
创业：The Start-up of You: Adapt to the Future, Invest in Yourself, and Transform Your Career

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

» Solve this problem

这题思路很简单，这个算法里很巧妙地用了当l1 or l2是null的时候用0来代替的做法，很简洁。

另外还要注意c＋＋里面指针的运算，要新开辟node呢。

	/**
	* Definition for singly-linked list.
	* struct ListNode {
	* int val;
	* ListNode *next;
	* ListNode(int x) : val(x), next(NULL) {}
	* };
	*/
	class Solution {
	public:
	ListNode *addTwoNumbers(ListNode *l1, ListNode *l2) {
	// Start typing your C/C++ solution below
	// DO NOT write int main() function
	ListNode *res=NULL, *tail=NULL;
	ListNode *L1=l1, *L2=l2;
	int carry=0;
	int sum=0;
	while(L1!=NULL||L2!=NULL||carry!=0)
	{
	int num1=(L1==NULL)? 0 :L1->val;
	int num2=(L2==NULL)? 0 :L2->val;
	sum=num1+num2+carry;
	carry=sum/10;
	sum%=10;
	if(res==NULL)
	{
	res=new ListNode(sum);
	tail=res;;
	}
	else
	{
	tail->next=new ListNode(sum);
	tail=tail->next;
	}
	L1=(L1==NULL)? NULL :L1->next;
	L2=(L2==NULL)? NULL :L2->next;
	}
	return res;
	}
	};

view raw add two numbers hosted with ❤ by GitHub