Leetcode 445. Add Two Numbers II

文章作者：Tyan
博客：noahsnail.com  |  CSDN  |  简书

1. Description

2. Solution

/**
 * 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) {
        stack<int> s1, s2;
        ListNode* current = l1;
        while(current) {
            s1.push(current->val);
            current = current->next;
        }
        current = l2;
        while(current) {
            s2.push(current->val);
            current = current->next;
        }
        int carry = 0;
        int sum = 0;
        ListNode* pre = nullptr;
        while(!s1.empty() || !s2.empty()) {
            sum = 0;
            if(!s1.empty()) {
                sum += s1.top();
                s1.pop();
            }
            if(!s2.empty()) {
                sum += s2.top();
                s2.pop();
            }
            sum += carry;
            carry = sum>9?1:0;
            current = new ListNode(sum % 10);
            current->next = pre;
            pre = current;
        }
        if(carry) {
            current = new ListNode(1);
            current->next = pre;
        }
        return current;
    }
};

Reference

1. https://leetcode.com/problems/add-two-numbers-ii/description/