leetcode_add two numbers

题目

Add two numbers

解题

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     struct ListNode *next;
 * };
 */
struct ListNode* addTwoNumbers(struct ListNode* l1, struct ListNode* l2) {
    int carry = 0;
    struct ListNode * ans = (struct ListNode *) malloc(sizeof(struct ListNode));
    struct ListNode * q = (struct ListNode *) malloc(sizeof(struct ListNode)); // 移位指针
    ans->next = NULL; // 链表的最后一个节点为NULL，否则遍历的时候会出现野指针
    q = ans;
    
    while(l1 || l2 || carry)
    {
        struct ListNode * p = (struct ListNode *) malloc(sizeof(struct ListNode));
        p->val = ((l1 ? l1->val:0) + (l2 ? l2->val:0) + carry) % 10;
        carry = ((l1 ? l1->val:0) + (l2 ? l2->val:0) + carry) / 10;
        p->next = q->next;
        q->next = p;
        q = q->next;
        l1 = l1 ? l1->next : l1;
        l2 = l2 ? l2->next : l2;
    }
    ans = ans->next;
    return ans;
}