leetcode8/MergeTwoSortedList.java at master · 1code/leetcode8 · GitHub

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
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
//Without sentry
public class Solution {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        // Start typing your Java solution below
        // DO NOT write main() function
        ListNode head = null, cur = null;
        while(l1 != null || l2 != null){
            ListNode next = null;
            if(l1 == null){
                if(head == null)
                    head = l2;
                else
                    cur.next = l2;
                break;
            }
            else if(l2 == null){
                if(head == null)
                    head = l1;
                else
                    cur.next = l1;
                break;
            }
            else if(l1.val > l2.val){
                next = l2;
                l2 = l2.next;
            }
            else{
                next = l1;
                l1 = l1.next;
            }
            if(head == null){
                head = next;
                cur = head;
            }
            else{
                cur.next = next;
                cur = cur.next;
            }
        }
        return head;
    }
}


/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
//Use a sentry
public class Solution {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        // Start typing your Java solution below
        // DO NOT write main() function
        ListNode sen = new ListNode(0);
        ListNode head = sen;
        while(l1 != null && l2 != null){
            if(l1.val < l2.val){
                sen.next = l1;
                l1 = l1.next;
                sen = sen.next;
            }
            else{
                sen.next = l2;
                l2 = l2.next;
                sen = sen.next;
            }
        }
        sen.next = l1 == null?l2:l1;
        return head.next;
    }
}