2.|2. Add Two Numbers

题目 You are given two non-empty linked lists representing two non-negative integers. 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.
You may assume the two numbers do not contain any leading zero, except the number 0 itself.

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

思路 第一种:恢复输入的两个数,然后相加,再转换回去。这种方法会遇到数值范围的问题,不予考虑。
第二种:由于数字是以个位开头的,可以直接相加进位到下一位,最后如果多出进位的话再加一位即可。
实现
/** * 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) { int ones = 0; int tens = 0; int rlt = 0; ListNode* ans; ListNode* last = NULL; while(l1!=NULL || l2!=NULL){ if(l1 == NULL){ rlt = l2->val + tens; l2 = l2->next; } else if(l2 == NULL){ rlt = l1->val + tens; l1 = l1->next; } else{ rlt = l1->val + l2->val + tens; l1 = l1->next; l2 = l2->next; } ones = rlt % 10; tens = rlt / 10; ListNode* node = new ListNode(ones); if(last == NULL){ ans = node; last = node; } else{ last->next = node; last = node; } } if(tens>0){ ListNode* node = new ListNode(tens); last->next = node; } return ans; } };

【2.|2. Add Two Numbers】主要考察对于链表的理解,不多说了。

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