LeetCode-2-两数相加-C语言

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该博客围绕LeetCode第2题两数相加，运用C语言进行解答。聚焦信息技术领域，涉及算法实现与C语言编程，为解决相关算法问题提供思路。

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/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     struct ListNode *next;
 * };
 */
typedef struct ListNode Node;

struct ListNode* addTwoNumbers(struct ListNode* l1, struct ListNode* l2) {
    int flag = 0;
    int tmp = 0;
    Node head;/* a dummy node in local, set as a head node, needs return node.next */
    Node *rear = &head;
    
    /* if l2 or l1 not NULL or flag!=0, will add node to the list */
    while(l1 || l2 || flag){
        
        /* get current value */
        tmp = (l1 ? l1->val : 0) + (l2 ? l2->val : 0) + flag;
        flag = 0;
        
        /* if need carry, set carry flag */
        if(tmp >= 10){
            flag = 1;
            tmp -= 10;
        }
        
        /* use nodes of l1 firstly */
        if(l1){
            l1->val = tmp;
            rear->next = l1;        
        }else if(l2){/* if l1 is NULL, use nodes of l2 */
            l2->val = tmp;
            rear->next = l2;
        }else{ /* if both l1 and l2 are NULL, malloc a node */
            Node *node = (Node *)malloc(sizeof(Node));
            node->val = tmp;
            node->next = NULL;/* set malloc node pointer NULL, remember this, cause always make mistakes here. */
            rear->next = node;
        }
        
        rear = rear->next;
        
        if(l1)
            l1 = l1->next;
        if(l2)
            l2 = l2->next;
    }
    
    return head.next;
    
}