21 Merge Two Sorted Lists
1. Question
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.
Example:
Input:
1->2->4, 1->3->4
Output:
1->1->2->3->4->4
2. Implementation
/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) { val = x; }
* }
*/
class Solution {
public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
ListNode dummy = new ListNode(0);
ListNode p1 = l1, p2 = l2, curNode = dummy;
while (p1 != null && p2 != null) {
if (p1.val < p2.val) {
curNode.next = p1;
p1 = p1.next;
}
else {
curNode.next = p2;
p2 = p2.next;
}
curNode = curNode.next;
}
if (p1 != null) {
curNode.next = p1;
}
else {
curNode.next = p2;
}
return dummy.next;
}
}
3. Time & Space Complexity
时间复杂度: O(n), 空间复杂度O(1)
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