I have a time limit exceeded error for my conditional statement

Question

leetcode problem: You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order, and each of their nodes contains a single digit. Add the two numbers and return the sum as a linked list.

You may assume the two numbers do not contain any leading zero, except the number 0 itself.

struct ListNode* addTwoNumbers(struct ListNode* l1, struct ListNode* l2){
    struct ListNode *head = malloc(sizeof(struct ListNode));
    head->next = NULL;
    struct ListNode *temp = head;
    int carry = 0;
    int x, y;
    while (l1 != NULL || l2 != NULL || carry != 0) {
        temp->next = malloc(sizeof(struct ListNode));
        int sum = (l1 != NULL ? l1->val : 0) + (l2 != NULL ? l2->val : 0) + carry;
        // if (l1 != NULL) x = l1->val;
        // if (l2 != NULL) y = l2->val;
        // int sum = x + y + carry;
        temp->next->val = (sum % 10);
        carry = sum / 10;
        temp->next->next = NULL;
        temp = temp->next;
        if (l1 != NULL) l1 = l1->next;
        if (l2 != NULL) l2 = l2->next;
    }
    temp->next = NULL;
    return (head->next);
}

This is my code and It was able to be passed. However, If I use variables x and y to get a sum of l1->val and l2->val-commenting "int sum = (l1 != NULL ? l1->val : 0) + (l2 != NULL ? l2->val : 0) + carry;" this part out , like

    // if (l1 != NULL) x = l1->val;
    // if (l2 != NULL) y = l2->val;
    // int sum = x + y + carry;

or

    x = l1 != NULL ? l1->val : 0;
    y = l2 != NULL ? l2->val : 0;

It causes a time limit exceeded error. Can anyone please explain what is wrong?

you already calculate the sum, why are you trying to calculate it again. YOu should not be writing the newlist inside the read loop, you should write it in a second loop after you calculate the sum — pm100, Feb 21 '22 at 05:33
why do you not use the first node (head)? how will you free that node later when there is no prev ptr and you return head->next — AndersK, Feb 21 '22 at 05:57
@pm100 oh, my question was that when I use the second and third conditional state instead of the first one(commenting. it), it's time limit exceeded! — Hans, Feb 21 '22 at 06:18
@AndersK I've set temp node that has an address of head node as a dummy node to store information. I only use head node to return the starting linked list. Because It didn't give me errors in regards to not freeing allocated memory, I didn't consider freeing the memory. would it be better if I free temp node just before return state? — Hans, Feb 21 '22 at 06:21
In the version with if statements, when corresponding node pointers are null, x and/or y are not initialised or contain previous garbage values instead of zeros — n. m. could be an AI, Feb 21 '22 at 06:48
@n.1.8e9-where's-my-sharem. WOW YOU'RE SO RIGHT. when I initialize x and y, it works. But when l1 and l2 are not null, wouldn't x and y be initialized as 0 according to my second conditional statement? — Hans, Feb 21 '22 at 07:24
oh I meant the third conditional statement -> "x = l1 != NULL ? l1->val : 0;" It initializes variable x when l1 is not a NULL but it generates same error as the second conditional statement. What am I missing? — Hans, Feb 21 '22 at 08:53

I have a time limit exceeded error for my conditional statement

0 Answers0