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// 445. Add Two Numbers II
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
/*
* given two non-empty linked lists representing two non-negative integers. the
* most significant digit comes first and each of their nodes contains a single
* digit. add the two numbers and return the same as a linked list. you may
* assume the two numbers do not contain any leading zero, except the number 0
* itself.
*/
struct ListNode {
int val;
struct ListNode *next;
};
static int append(struct ListNode *l1, struct ListNode *l2, int missing) {
int carry, val;
if (!l1)
return 0;
if (!missing) {
carry = append(l1->next, l2->next, 0);
val = l1->val + l2->val + carry;
} else {
carry = append(l1->next, l2->next, -1);
val = l1->val + carry;
}
l1->val = val % 10;
return val / 10;
}
static int length(struct ListNode *n) {
int len;
for (len = 0; n; n = n->next)
len++;
return len;
}
static void swap(struct ListNode **p1, struct ListNode **p2) {
struct ListNode *tmp;
tmp = *p1;
*p1 = *p2;
*p2 = tmp;
}
struct ListNode *addTwoNumbers(struct ListNode *l1, struct ListNode *l2) {
int len1, len2, carry;
struct ListNode *head;
len1 = length(l1);
len2 = length(l2);
if (len1 < len2)
swap(&l1, &l2);
carry = append(l1, l2, abs(len1 - len2));
if (carry) {
if (!(head = malloc(sizeof(struct ListNode))))
return head;
head->val = 1;
head->next = l1;
}
return l1;
}
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