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LoeiJe

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leetcode-2

leetcode 2

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// 我写的....
/**
 * 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) {
        ListNode *first_l1 = l1, *first_l2 = l2;
        //ListNode *ans, *root;
        ListNode *ans = new ListNode(0);
        ListNode *root = ans;
        int flag = 0; // 进位标记，初始0
        int aux = 0;
        int x, y;
        while(first_l1 || first_l2) {
            if(first_l1) x = first_l1->val;
            else x = 0;
            if(first_l2) y = first_l2->val;
            else y = 0;
            aux = x + y + flag;
            flag = aux / 10; aux = aux % 10;

            ListNode *temp = new ListNode(aux);
            ans->next = temp;
            ans = ans->next;

            if(first_l1)  first_l1 = first_l1->next;
            if(first_l2)  first_l2 = first_l2->next;
        }
        if(flag) {
            ListNode *temp = new ListNode(1);
            ans->next = temp;
        }
        return root->next;
    }
};

// 别人写的
/**
 * 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) {
        ListNode ans(0), *p = &ans;
        int aux = 0, flag = 0;
        while(l1 || l2 || flag) {
            aux = 0;
            if(l1) aux += l1->val;
            if(l2) aux += l2->val;
            aux += flag;
            flag = aux / 10;
            aux = aux % 10;

            ListNode *new_node = l1 ? l1 : l2; // 不新建节点 使用原数据节点
            if(nullptr == new_node) new_node = new ListNode(aux);

            new_node->val = aux;    //使用元数据节点时 重新赋值
            p->next = new_node;
            p = p->next;
            if(l1) l1 = l1->next;
            if(l2) l2 = l2->next;
        }
        return ans.next;
    }
};
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