難度: Easy
類型: Linked list,Recursion
CPP程式下載: 21.cpp
Topic:
You are given the heads of two sorted linked lists list1 and list2.
Merge the two lists into one sorted list. The list should be made by splicing together the nodes of the first two lists.
Return the head of the merged linked list.
Example 1:
Input: list1 = [1,2,4], list2 = [1,3,4] Output: [1,1,2,3,4,4]
Example 2:
Input: list1 = [], list2 = [] Output: []
Example 3:
Input: list1 = [], list2 = [0] Output: [0]
Constraints:
- The number of nodes in both lists is in the range
[0, 50]. -100 <= Node.val <= 100- Both
list1andlist2are sorted in non-decreasing order.
Consideration:
Linked List combined.
1. Compare and add the smaller one. Move pointer to next. When one list is ended, add the rest of another list.
2. If both lists empty, return nullptr.
Code:
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode() : val(0), next(nullptr) {}
* ListNode(int x) : val(x), next(nullptr) {}
* ListNode(int x, ListNode *next) : val(x), next(next) {}
* };
*/
class Solution {
public:
ListNode* mergeTwoLists(ListNode* list1, ListNode* list2) {
//int iSize1=list1.size();
//int iSize2=list2.size();
//int i=0,j=0;
ListNode* outlist=nullptr;
ListNode* outlistHead=nullptr;
ListNode* list1tmp=list1;
ListNode* list2tmp=list2;
if (list1==nullptr) {
return list2;
}
else if (list2==nullptr) {
return list1;
}
else
{
while (1) {
if (list2->val<list1->val) {
if (outlistHead==nullptr) {
//cout << "list2->val=" << list2->val << "\n";
outlist=list2;
list2=list2->next;
outlistHead=outlist;
}
else {
//cout << "list2->val=" << list2->val << "\n";
outlist->next=list2;
list2=list2->next;
outlist=outlist->next;
}
}
else {
if (outlistHead==nullptr) {
outlist=list1;
list1=list1->next;
outlistHead=outlist;
}
else {
outlist->next=list1;
list1=list1->next;
outlist=outlist->next;
}
}
if (list1==nullptr)
{
outlist->next=list2;
//cout << "A:list2->val=" << list2->val << "\n";
return outlistHead;
}
else if (list2==nullptr)
{
outlist->next=list1;
return outlistHead;
}
}
}
}
};
Result:
https://leetcode.com/problems/merge-two-sorted-lists/submissions/1831161763/
https://leetcode.com/problems/merge-two-sorted-lists/submissions/1831161763/
Runtime
0msBeats100.00%
Memory
19.58MBBeats26.66%
