2. Add Two Numbers 大数运算

题目地址

注意长度不等时的情况

class Solution {public:    ListNode *addTwoNumbers(ListNode *l1, ListNode *l2) {        vector<int> v1, v2, v3;        while (l1 != NULL) {            v1.push_back(l1->val);            l1 = l1->next;        }        while (l2 != NULL) {            v2.push_back(l2->val);            l2 = l2->next;        }        int i = 0, j = 0, k = 0;        int carry = 0;        while (i < v1.size() && j < v2.size()) {            int now = (v1[i] + v2[j] + carry) % 10;            carry = (v1[i] + v2[j] + carry) / 10;            v3.push_back(now);            i++;            j++;        }        if (carry) {            if (i < v1.size()) {                while (i < v1.size()) {                    int now = (v1[i] + carry) % 10;                    carry = (v1[i] + carry) / 10;                    v3.push_back(now);                    i++;                }            } else if (j < v2.size()) {                while (j < v2.size()) {                    int now = (v2[j] + carry) % 10;                    carry = (v2[j] + carry) / 10;                    v3.push_back(now);                    j++;                }            }            if (carry) v3.push_back(carry);        } else {            while (i < v1.size()) v3.push_back(v1[i++]);            while (j < v2.size()) v3.push_back(v2[j++]);        }        ListNode *p = new ListNode(v3[0]);        ListNode *ans = p;        for (int k = 1; k < v3.size(); ++k) {            ListNode *temp = new ListNode(v3[k]);            p->next = temp;            p = temp;        }        return ans;    }};