LeetCode/2.add-two-numbers.cpp at master · samba9274/LeetCode · GitHub

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/*
 * @lc app=leetcode id=2 lang=cpp
 *
 * [2] Add Two Numbers
 *
 * https://leetcode.com/problems/add-two-numbers/description/
 *
 * algorithms
 * Medium (39.13%)
 * Likes:    20853
 * Dislikes: 4116
 * Total Accepted:    3M
 * Total Submissions: 7.7M
 * Testcase Example:  '[2,4,3]\n[5,6,4]'
 *
 * You are given two non-empty linked lists representing two non-negative
 * integers. The digits are stored in reverse order, and each of their nodes
 * contains a single digit. Add the two numbers and return the sum as a linked
 * list.
 *
 * You may assume the two numbers do not contain any leading zero, except the
 * number 0 itself.
 *
 *
 * Example 1:
 *
 *
 * Input: l1 = [2,4,3], l2 = [5,6,4]
 * Output: [7,0,8]
 * Explanation: 342 + 465 = 807.
 *
 *
 * Example 2:
 *
 *
 * Input: l1 = [0], l2 = [0]
 * Output: [0]
 *
 *
 * Example 3:
 *
 *
 * Input: l1 = [9,9,9,9,9,9,9], l2 = [9,9,9,9]
 * Output: [8,9,9,9,0,0,0,1]
 *
 *
 *
 * Constraints:
 *
 *
 * The number of nodes in each linked list is in the range [1, 100].
 * 0 <= Node.val <= 9
 * It is guaranteed that the list represents a number that does not have
 * leading zeros.
 *
 *
 */

// @lc code=start
/**
 * 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 *root = new ListNode(), *node = root;
        int carry = 0;
        while (l1 != nullptr && l2 != nullptr)
        {
            int sum = l1->val + l2->val + carry;
            carry = 0;
            if (sum >= 10)
            {
                carry++;
                sum %= 10;
            }
            node->next = new ListNode(sum);
            node = node->next;
            l1 = l1->next;
            l2 = l2->next;
        }
        while (l1 != nullptr)
        {
            int sum = l1->val + carry;
            carry = 0;
            if (sum >= 10)
            {
                carry++;
                sum %= 10;
            }
            node->next = new ListNode(sum);
            node = node->next;
            l1 = l1->next;
        }
        while (l2 != nullptr)
        {
            int sum = l2->val + carry;
            carry = 0;
            if (sum >= 10)
            {
                carry++;
                sum %= 10;
            }
            node->next = new ListNode(sum);
            node = node->next;
            l2 = l2->next;
        }
        if (carry)
            node->next = new ListNode(carry);
        return root->next;
    }
};
// @lc code=end