LeetCode [21] Merge Two Sorted Lists

21. Merge Two Sorted Lists

Easy

Merge two sorted linked lists and return it as a new sorted list. The new list should be made by splicing together the nodes of the first two lists.

 

Example 1:

Input: l1 = [1,2,4], l2 = [1,3,4]
Output: [1,1,2,3,4,4]

Example 2:

Input: l1 = [], l2 = []
Output: []

Example 3:

Input: l1 = [], l2 = [0]
Output: [0]

 

Constraints:

• The number of nodes in both lists is in the range [0, 50].
• -100 <= Node.val <= 100
• Both l1 and l2 are sorted in non-decreasing order.

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class Solution { public: ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) { ListNode* H = new ListNode(0); ListNode* p = H; ListNode* p1 = l1; ListNode* p2 = l2; while(p1&&p2){ if(p1->val<=p2->val){ p->next = p1; p1 = p1->next; }else{ p->next = p2; p2 = p2->next; } p = p->next; } p->next = p1?p1:p2; return H->next; } };

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/** * Definition for singly-linked list. * public class ListNode { * int val; * ListNode next; * ListNode() {} * ListNode(int val) { this.val = val; } * ListNode(int val, ListNode next) { this.val = val; this.next = next; } * } */ class Solution { public ListNode mergeTwoLists(ListNode l1, ListNode l2) { ListNode head = new ListNode(); ListNode p = head; while(l1!=null && l2!=null){ if(l1.val<=l2.val){ p.next = l1; p = l1; l1 = l1.next; }else{ p.next = l2; p = l2; l2 = l2.next; } } if(l1!=null){ p.next = l1; } if(l2!=null){ p.next = l2; } return head.next; } }