2. 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
就两个链表相加。。。。。练手题咯

/** * 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) {        long long int sum1, sum2, sum;        sum1 = sum2 = sum = 0;        for(int i = 0; l1 != NULL; l1 = l1 -> next, ++i)        {            sum1 += l1 -> val * pow(10, i);        }        for(int i = 0; l2 != NULL; l2 = l2 -> next, ++i)        {            sum2 += l2 -> val * pow(10, i);        }        sum = sum1 + sum2;        ListNode *g = new ListNode(sum - (sum / 10) * 10);        ListNode *n = g;        ListNode *tt;        tt = n;        sum = sum / 10;        while(sum > 0)        {            ListNode *t = new ListNode(sum - (sum / 10) * 10);            tt -> next = t;            tt = t;            sum = sum / 10;        }        return n;    }};