002 - Add Two Number

解碼

pointer 處理

程式碼

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
        ListNode* head = new ListNode();
        ListNode* cur = head;

        int sum = 0;
        while(1){
            if(l1 != nullptr){
                sum += l1->val;
                l1 = l1->next;
            }
            if(l2 != nullptr){
                sum += l2->val;
                l2 = l2->next;
            }

            cur->val = sum % 10;
            sum /= 10;
            //當沒有更大位數能加且不處理進位問題， break;
            if(l1 == nullptr && l2 == nullptr && sum == 0) break;
            cur->next = new ListNode();
            cur = cur->next;
        }
        return head;
    }
};