445.cpp

// vector.cpp
/**
 * 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) {
    vector<int> arr1, arr2;
    while (l1) {
      arr1.emplace_back(l1->val);
      l1 = l1->next;
    }
    while (l2) {
      arr2.emplace_back(l2->val);
      l2 = l2->next;
    }
    ListNode *p = new ListNode(0);
    int i, j, c = 0, val;
    for (i = arr1.size() - 1, j = arr2.size() - 1; i >= 0 || j >= 0 || c > 0;
         c = val / 10) {
      val = (i >= 0 ? arr1[i--] : 0) + (j >= 0 ? arr2[j--] : 0) + c;
      ListNode *node = new ListNode(val % 10);
      node->next = p->next;
      p->next = node;
    }
    return p->next;
  }
};