# Two Lists Sum Advanced ### Source - CC150 - [Add two numbers represented by linked lists | Set 2 - GeeksforGeeks](http://www.geeksforgeeks.org/sum-of-two-linked-lists/) ~~~ Given two numbers represented by two linked lists, write a function that returns sum list. The sum list is linked list representation of addition of two input numbers. Example Input: First List: 5->6->3 // represents number 563 Second List: 8->4->2 // represents number 842 Output Resultant list: 1->4->0->5 // represents number 1405 Challenge Not allowed to modify the lists. Not allowed to use explicit extra space. ~~~ ### 题解1 - 反转链表 在题 [Two Lists Sum | Data Structure and Algorithm](http://algorithm.yuanbin.me/zh-cn/linked_list/two_lists_sum.html) 的基础上改了下数位的表示方式，前者低位在前，高位在后，这个题的高位在前，低位在后。很自然地可以联想到先将链表反转，而后再使用 Two Lists Sum 的解法。 ### Reference - [Add two numbers represented by linked lists | Set 2 - GeeksforGeeks](http://www.geeksforgeeks.org/sum-of-two-linked-lists/)