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21_merge_two_sorted_list.cpp
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21_merge_two_sorted_list.cpp
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//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]
/**
* 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) {
if (!list1) return list2;
if (!list2) return list1;
if (list1->val < list2->val) {
list1->next = mergeTwoLists(list1->next, list2);
return list1;
} else {
list2->next = mergeTwoLists(list1, list2->next);
return list2;
}
}
};