Add Two Numbers

AddTwoNumbers.c

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

typedef struct ListNode ListNode;

struct ListNode* addTwoNumbers(struct ListNode* l1, struct ListNode* l2) {
	ListNode *l1cur, *l2cur, *ans, **anscur;
	int a, b, sum, carry;
	l1cur = l1;
	l2cur = l2;
	ans = NULL;
	anscur = &ans;
	carry = 0;
	while (l1cur != NULL || l2cur != NULL || carry != 0) {
		if (l1cur != NULL) {
			a = l1cur->val;
			l1cur = l1cur->next;
		}
		else {
			a = 0;
		}
		if (l2cur != NULL) {
			b = l2cur->val;
			l2cur = l2cur->next;
		}
		else {
			b = 0;
		}
		sum = a + b + carry;
		carry = sum >= 10;
		sum = carry ? sum - 10 : sum;
		(*anscur) = (ListNode*)malloc(sizeof(ListNode));
		(*anscur)->val = sum;
		(*anscur)->next = NULL;
		anscur = &((*anscur)->next);
	}
	return ans;
}