solves insertion sort list in java

Author: anishLearnsToCode

README.md

@@ -131,7 +131,7 @@
 | 144  | [Binary Tree Preorder Traversal](https://leetcode.com/problems/binary-tree-preorder-traversal)                                                            |                      [![Java](assets/java.png)](src/BinaryTreePreOrderTraversal.java) [![Python](assets/python.png)](python/binary_tree_preorder_traversal.py)                       |                                                                                                                                   |
 | 145  | [Binary Tree Postorder Traversal](https://leetcode.com/problems/binary-tree-postorder-traversal)                                                          |                     [![Java](assets/java.png)](src/BinaryTreePostorderTraversal.java) [![Python](assets/python.png)](python/binary_tree_postorder_traversal.py)                      |                                                                                                                                   |
 | 146  | [LRU Cache](https://leetcode.com/problems/lru-cache)                                                                                                      |                                                                    [![Java](assets/java.png)](src/LRUCache.java)                                                                     |                                                                                                                                   |
-| 147  | [Insertion Sort List](https://leetcode.com/problems/insertion-sort-list)                                                                                  |                                                                                                                                                                                      |                                                                                                                                   |
+| 147  | [Insertion Sort List](https://leetcode.com/problems/insertion-sort-list)                                                                                  |                                                                [![Java](assets/java.png)](src/InsertionSortList.java)                                                                |                                                                                                                                   |
 | 148  | [Sort List](https://leetcode.com/problems/sort-list)                                                                                                      |                                                                                                                                                                                      |                                                                                                                                   |
 | 150  | [Evaluate Reverse Polish Notation](https://leetcode.com/problems/evaluate-reverse-polish-notation)                                                        |                                                                                                                                                                                      |                                                                                                                                   |
 | 151  | [Reverse Words in a String](https://leetcode.com/problems/reverse-words-in-a-string)                                                                      |                                                                                                                                                                                      |                                                                                                                                   |

src/InsertionSortList.java

@@ -0,0 +1,29 @@
+// https://leetcode.com/problems/insertion-sort-list
+// T: O(n^2)
+// S: O(1)
+
+public class InsertionSortList {
+    public ListNode insertionSortList(ListNode head) {
+        if (head == null || head.next == null) return head;
+
+        ListNode newHead = new ListNode(0);
+        ListNode pre = newHead;
+        ListNode next;
+
+        for (ListNode cur = head ; cur != null ; ) {
+            next = cur.next;
+
+            while (pre.next != null && pre.next.val < cur.val) {
+                pre = pre.next;
+            }
+
+            //insert between pre and pre.next
+            cur.next = pre.next;
+            pre.next = cur;
+            pre = newHead;
+            cur = next;
+        }
+
+        return newHead.next;
+    }
+}