Problem
You are given the heads of two sorted linked lists list1 and list2.
Merge the two lists in a 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.
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.
Example:
1
2
Input: list1 = [1,2,4], list2 = [1,3,4]
Output: [1,1,2,3,4,4]
Solution
c++
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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) {}
};
ListNode *merge_two_sorted_list::mergeTwoLists(ListNode *list1, ListNode *list2) {
if (list1 == nullptr) {
return list2;
}
if (list2 == nullptr) {
return list1;
}
ListNode* listNode = nullptr;
ListNode* head = nullptr;
while (true) {
if (list1->val <= list2->val) {
if (listNode == nullptr) {
listNode = list1;
head = list1;
} else {
listNode->next = list1;
listNode = list1;
}
list1 = list1->next;
if (list1 == nullptr) {
listNode->next = list2;
break;
}
} else {
if (listNode == nullptr) {
listNode = list2;
head = listNode;
} else {
listNode->next = list2;
listNode = list2;
}
list2 = list2->next;
if (list2 == nullptr) {
listNode->next = list1;
break;
}
}
}
return head;
}
References
https://leetcode.com/problems/merge-two-sorted-lists/?envType=study-plan&id=level-1