leetcode 21 -- Merge Two Sorted Lists
阿新 • • 發佈:2017-07-24
tro leet lan 常見 ber 題目 tty Language node
Merge Two Sorted Lists
題目:
Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.
題意:
合並兩個排序過的鏈表
思路:
這是個非經常見的問題,須要註意的就是給定兩個鏈表是否為空。
代碼:
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
if(l1 == NULL && l2 == NULL){
return NULL;
}else if(l1 == NULL && l2 != NULL){
return l2;
}else if(l1 != NULL && l2 == NULL){
return l1;
}
//指定頭節點
ListNode *new_head = NULL;
if(l1->val < l2->val){
new_head = l1;
l1 = l1->next;
}else{
new_head = l2;
l2 = l2->next;
}
ListNode *p = new_head;
while(l1 != NULL && l2 != NULL){
if(l1->val < l2->val){
p->next = l1;
p = p->next;
l1 = l1->next;
}else{
p->next = l2;
p = p->next;
l2 = l2->next;
}
}
//接上余下的鏈表段
if(l1 != NULL){
p->next = l1;
}else{
p->next = l2;
}
return new_head;
}
};
leetcode 21 -- Merge Two Sorted Lists