leetcode 2. 两数相加

我的解题

#include <bits/stdc++.h>
using namespace std;
/**
 * 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) {}
 * };
 */

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 dummyNode { 0 };
        ListNode *tail = &dummyNode;
        int addOn = 0; // 进位
        int sum = 0; // 两个节点的和
        int val = 0; // 当前节点的值
        while (l1 && l2)
        {
            sum = l1->val + l2->val + addOn;
            val = sum % 10;
            addOn = sum >= 10 ? 1 : 0; // 进位这可能进1或0
            tail->next = new ListNode(val);
            tail = tail->next;
            l1 = l1->next;
            l2 = l2->next;
        }
        if (l1 || l2)
        {
            ListNode *temp = l1 ? l1 : l2;
            while (temp)
            {
                sum = temp->val + addOn;
                val = sum % 10;
                addOn = sum >= 10 ? 1 : 0; // 进位这可能进1或0
                tail->next = new ListNode(val);
                tail = tail->next;
                temp = temp->next;
            }
        }
        if (addOn)
        {
            tail->next = new ListNode(addOn);
        }
        return dummyNode.next;
    }
};

int main()
{

}
// g++ test.cpp --std=c++11 -pedantic -Wall -Wextra -g

官方解题

#include <bits/stdc++.h>
using namespace std;
/**
 * 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) {}
 * };
 */

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 = nullptr, *tail = nullptr;
        int carry = 0;
        while (l1 || l2)
        {
            int n1 = l1 ? l1->val : 0;
            int n2 = l2 ? l2->val : 0;
            int sum = n1 + n2 + carry;
            if (!head)
            {
                head = tail = new ListNode(sum % 10);
            }
            else
            {
                tail->next = new ListNode(sum % 10);
                tail = tail->next;
            }
            carry = sum / 10;
            if (l1)
            {
                l1 = l1->next;
            }
            if (l2)
            {
                l2 = l2->next;
            }
        }
        if (carry > 0)
        {
            tail->next = new ListNode(carry);
        }
        return head;
    }
};

int main()
{

}
// g++ test.cpp --std=c++11 -pedantic -Wall -Wextra -g