C代码
/**
* Definition for singly-linked list.
* struct ListNode {
*int val;
*struct ListNode *next;
* };
*/struct ListNode* mergeTwoLists(struct ListNode* list1, struct ListNode* list2){
struct ListNode *dummy = NULL;
struct ListNode *head = NULL;
if (list1 == NULL) {
return list2;
}if (list2 == NULL) {
return list1;
}if(list1->val <= list2->val) {
dummy = list1;
list1 = list1->next;
} else {
dummy = list2;
list2 = list2->next;
}
head = dummy;
while(list1 != NULL && list2 != NULL) {
if (list1->val >= list2->val) {
dummy->next = list2;
list2 = list2->next;
} else {
dummy->next = list1;
list1 = list1->next;
}
dummy = dummy->next;
}
if (list1 != NULL) {
dummy->next = list1;
}
if (list2 != NULL) {
dummy->next = list2;
}
return head;
}
注意点
dummy和head节点的初始化,需要移动list1或者list2;- 遍历操作感觉比较冗余(头初始化list1或者list2,后去遍历代码又移动一次),代码需要优化;
文章图片
DUMMY C代码优化版本
/**
* Definition for singly-linked list.
* struct ListNode {
*int val;
*struct ListNode *next;
* };
*/struct ListNode* mergeTwoLists(struct ListNode* list1, struct ListNode* list2){
struct ListNode *dummy = NULL;
struct ListNode *head = NULL;
if (list1 == NULL) {
return list2;
}if (list2 == NULL) {
return list1;
}head = calloc(1, sizeof(struct ListNode));
dummy = head;
while(list1 != NULL && list2 != NULL) {
if (list1->val >= list2->val) {
dummy->next = list2;
list2 = list2->next;
} else {
dummy->next = list1;
list1 = list1->next;
}
dummy = dummy->next;
}
if (list1 != NULL) {
dummy->next = list1;
}
if (list2 != NULL) {
dummy->next = list2;
}
dummy = head->next;
free(head);
head = NULL;
return dummy;
}
思路
- 新建头节点空间
head; - 最终返回
head->next,来统一list1与list2的移动逻辑到while循环内;
文章图片
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