Add time and space complexity analysis for Topic 2 solutions

Author: dkhien

Topic2_LinkedList/dkhien/01ReverseLinkedList.java

@@ -1,3 +1,6 @@
+// Time Complexity: O(n)
+// Space Complexity: O(1)
+
 class Solution {
     public ListNode reverseList(ListNode head) {
         if (head == null) return null;

Topic2_LinkedList/dkhien/02MergeTwoSortedLists.java

@@ -1,13 +1,6 @@
-/**
- * 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; }
- * }
- */
+// Time Complexity: O(n)
+// Space Complexity: O(1)
+
 class Solution {
     public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
         ListNode result = new ListNode();

Topic2_LinkedList/dkhien/03ReorderList.java

@@ -1,13 +1,6 @@
-/**
- * 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; }
- * }
- */
+// Time Complexity: O(n)
+// Space Complexity: O(n)
+
 class Solution {
     public void reorderList(ListNode head) {
         List<ListNode> nodeList = new ArrayList<>();

Topic2_LinkedList/dkhien/04RemoveNthNodeFromEndOfList.java

@@ -1,13 +1,6 @@
-/**
- * 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; }
- * }
- */
+// Time Complexity: O(n)
+// Space Complexity: O(1)
+
 class Solution {
     public ListNode removeNthFromEnd(ListNode head, int n) {
         if (head == null || head.next == null) return null;

Topic2_LinkedList/dkhien/05CopyListWithRandomPointer.java

@@ -1,17 +1,5 @@
-/*
-// Definition for a Node.
-class Node {
-    int val;
-    Node next;
-    Node random;
-
-    public Node(int val) {
-        this.val = val;
-        this.next = null;
-        this.random = null;
-    }
-}
-*/
+// Time Complexity: O(n)
+// Space Complexity: O(n)
 
 class Solution {
     public Node copyRandomList(Node head) {

Topic2_LinkedList/dkhien/06AddTwoNumbers.java

@@ -1,13 +1,6 @@
-/**
- * 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; }
- * }
- */
+// Time Complexity: O(n)
+// Space Complexity: O(1)
+
 class Solution {
     public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
         ListNode dummy = new ListNode();

Topic2_LinkedList/dkhien/07LinkedListCycle.java

@@ -1,17 +1,10 @@
-/**
- * Definition for singly-linked list.
- * class ListNode {
- *     int val;
- *     ListNode next;
- *     ListNode(int x) {
- *         val = x;
- *         next = null;
- *     }
- * }
- */
+// Time Complexity: O(n)
+// Space Complexity: O(1)
+
 public class Solution {
     public boolean hasCycle(ListNode head) {
-        if (head == null) return false;
+        if (head == null)
+            return false;
         ListNode slow = head;
         ListNode fast = head;