c++-add two numbers 两个链表相加

题目描述

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

这道题考察的是链表相加，最简单的方法就是用新的链表来存入数据，因此关键点在于链表的新建：

利用new来开辟存储空间，也就是堆：

/**
 * 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 temp;
        int flag=0;
        ListNode* p=l1;
        ListNode* q=l2;
        ListNode* res_head = new ListNode(-1);
        ListNode* res_tmp=res_head;
        
        while(p!=NULL || q!=NULL || flag){
            temp=(p?p->val:0)+(q?q->val:0)+flag;
            flag=0;
            if(temp>=10){
                temp-=10;
                flag=1;
            }
            ListNode* tmp = new ListNode(temp);
            res_tmp->next=tmp;
            res_tmp=res_tmp->next;
            if(p) p = p->next;
            if(q) q = q->next;
        }
        return res_head->next;
    }
};