LeetCode2——Add Two Numbers

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

难度系数：

中等

实现

ListNode *addTwoNumbers(ListNode *l1, ListNode *l2) {
    int add = 0;
    int sum = 0;
    ListNode* head = NULL;
    ListNode* curr = NULL;
    while (l1 || l2 || add > 0) {
        if (l1 == NULL && l2 == NULL) {
            sum = 0;
        }
        else if (l1 == NULL) {
            sum = l2->val;
            l2 = l2->next;
        } else if (l2 == NULL) {
            sum = l1->val;
            l1 = l1->next;
        } else {
            sum = l1->val + l2->val;
            l1 = l1->next;
            l2 = l2->next;
        }
        sum += add;
        ListNode *ln = new ListNode(sum%10);
        add = sum / 10;
        if (head == NULL) {
            head = ln;
        }
        if (curr != NULL) {
            curr->next = ln;
        }
        curr = ln;
    }
    return head;
}