21. Merge Two Sorted Lists
Merge two sorted linked lists and return it as a sorted list. The list should be made by splicing together the nodes of the first two lists.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
| 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.
Solution#
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
| /**
* 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 node1 = l1;
ListNode node2 = l2;
ListNode node3 = new ListNode(-1);
ListNode head = node3;
ListNode prev = null;
while (node1 != null || node2 != null) {
if (node1 != null && node2 != null) {
if (node1.val < node2.val) {
ListNode node = new ListNode(node1.val);
node3.next = node;
prev = node3;
node1 = node1.next;
} else {
ListNode node = new ListNode(node2.val);
node3.next = node;
prev = node3;
node2 = node2.next;
}
} else if (node1 != null) {
ListNode node = new ListNode(node1.val);
node3.next = node;
prev = node3;
node1 = node1.next;
} else if (node2 != null) {
ListNode node = new ListNode(node2.val);
node3.next = node;
prev = node3;
node2 = node2.next;
}
node3 = node3.next;
}
return head.next;
}
}
|
Solution 2021-11-21#
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
| /**
* 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 curr = new ListNode();
ListNode root = curr;
while (l1 != null || l2 != null) {
if (l1 != null && l2 != null) {
if (l1.val < l2.val) {
ListNode node = new ListNode(l1.val);
curr.next = node;
curr = curr.next;
l1 = l1.next;
} else {
ListNode node = new ListNode(l2.val);
curr.next = node;
curr = curr.next;
l2 = l2.next;
}
} else if (l1 != null) {
ListNode node = new ListNode(l1.val);
curr.next = node;
curr = curr.next;
l1 = l1.next;
} else {
ListNode node = new ListNode(l2.val);
curr.next = node;
curr = curr.next;
l2 = l2.next;
}
}
return root.next;
}
}
|