2-Add Two Numbers @LeetCode

2-Add Two Numbers @LeetCode

题目

思路

题目中得到的信息有：

C算法

/**
* Definition for singly-linked list.
* struct ListNode {
*     int val;
*     struct ListNode *next;
* };
*/
struct ListNode* addTwoNumbers(struct ListNode* l1, struct ListNode* l2) {
struct ListNode *ret, *p, *prev;
p = ret = prev = NULL;
int flag = 0;
//先是两个整数相加
while((l1 != NULL) && (l2 != NULL) ) {
p = (struct ListNode *)malloc(sizeof(struct ListNode));
p->val = l1->val + l2->val + flag;
flag = p->val / 10;
p->val -= (flag > 0 ? 10 : 0);
if (prev != NULL) prev->next = p;
prev = p;
if (ret == NULL) ret = p;
l1 = l1->next;
l2 = l2->next;
}
//若是l1还有结点，添加上去
while(l1 != NULL) {
p = (struct ListNode *)malloc(sizeof(struct ListNode));
p->val = l1->val  + flag;
flag = p->val / 10;
p->val -= (flag > 0 ? 10 : 0);
l1 = l1->next;
if (prev != NULL) prev->next = p;
if (ret == NULL) ret = p;
prev->next = p;
prev = p;
}
//若是l2还有结点，添加上去
while(l2 != NULL) {
p = (struct ListNode *)malloc(sizeof(struct ListNode));
p->val = l2->val  + flag;
flag = p->val / 10;
p->val -= (flag > 0 ? 10 : 0);
l2 = l2->next;
if (prev != NULL) prev->next = p;
if (ret == NULL) ret = p;
prev->next = p;
prev = p;
}
//最后可能会有进位，要考虑到
if (flag != 0) {
p = (struct ListNode *)malloc(sizeof(struct ListNode));
p->val = flag;
prev->next = p;
prev = p;
flag = 0;
}
prev->next = NULL;
return ret;
}

结果