-
Notifications
You must be signed in to change notification settings - Fork 0
Expand file tree
/
Copy pathListNode.java
More file actions
74 lines (58 loc) · 1.85 KB
/
ListNode.java
File metadata and controls
74 lines (58 loc) · 1.85 KB
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
import java.util.*;
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; }
public static void main(String[] args) {
// Create a sample linked list 1 -> 2 -> 3 -> 4 -> 5
ListNode head = new ListNode(1);
head.next = new ListNode(2);
head.next.next = new ListNode(3);
head.next.next.next = new ListNode(4);
head.next.next.next.next = new ListNode(5);
System.out.println("Original list: ");
RevLinkList.printList(head);
// Reverse it
RevLinkList revLinkList = new RevLinkList();
ListNode reversed = revLinkList.reverseList(head);
System.out.println("Reversed: ");
RevLinkList.printList(reversed);
}
}
class RevLinkList {
public ListNode reverseList(ListNode head) {
ListNode prev = null;
// ListNode current = head;
while (head != null) {
ListNode next = head.next;
head.next = prev;
prev = head;
head = next;
}
return prev;
}
public static void printList(ListNode head) {
ListNode temp = head;
while (temp != null) {
System.out.print(temp.val + " ");
temp = temp.next;
}
System.out.println();
}
}
/*
* Can use 3 pointers
* - prev = null
* - curr = head
* - next = null
* While curr is not null:
* - store next node of curr in next
* - reverse the next ponter of curr to point to prev
* - move prev to curr (for next iteration)
* - move curr to next
* Update the head
* - at end of loop, prev will be the new head of the reversed list
* Return prev as New Head
*/