add 369 java

Author: yennanliu

README.md

@@ -417,7 +417,7 @@
 234| [Palindrome Linked List](https://leetcode.com/problems/palindrome-linked-list/)|[Python](./leetcode_python/Linked_list/palindrome-linked-list.py), [Java](./leetcode_java/src/main/java/LeetCodeJava/LinkedList/PalindromeLinkedList.java)| _O(n)_ | _O(1)_| Easy|linked list,`amazon`,`fb`| OK (4) 
 237| [Delete Node in a Linked List](https://leetcode.com/problems/delete-node-in-a-linked-list/)| [Python](./leetcode_python/Linked_list/delete-node-in-a-linked-list.py)| _O(1)_| _O(1)_| Easy| LintCode, apple | OK * (1) (but again) 
 328| [Odd Even Linked List](https://leetcode.com/problems/odd-even-linked-list/)|[Python](./leetcode_python/Linked_list/odd-even-linked-list.py) | _O(n)_  | _O(1)_   | Medium    |`basic` | OK** (2)
-369| [Plus One Linked List](https://leetcode.com/problems/plus-one-linked-list/)| [Python](./leetcode_python/Linked_list/plus-one-linked-list.py) | _O(n)_  | _O(1)_ | Medium | 🔒, `basic`, `trick` | AGAIN* (2)
+369| [Plus One Linked List](https://leetcode.com/problems/plus-one-linked-list/)| [Python](./leetcode_python/Linked_list/plus-one-linked-list.py), [Java](./leetcode_java/src/main/java/LeetCodeJava/LinkedList/PlusOneLinkedList.java) | _O(n)_  | _O(1)_ | Medium | 🔒, linkedlist,  `basic`, google | AGAIN****** (3)
 445| [Add Two Numbers II](https://leetcode.com/problems/add-two-numbers-ii/)| [Python](./leetcode_python/Linked_list/add-two-numbers-ii.py) | _O(m + n)_ | _O(m + n)_| Medium  |`trick`, linked list, string,`good basic`, `amazon`| AGAIN*** (3)
 725 | [Split Linked List in Parts](https://leetcode.com/problems/split-linked-list-in-parts/) | [Python](./leetcode_python/Linked_list/split-linked-list-in-parts.py)  | _O(n + k)_ | _O(1)_ | Medium |mod, split linked list, linked list, good trick,`amazon`| AGAIN************ (6) (again)
 817 | [Linked List Components](https://leetcode.com/problems/linked-list-components/) | [Python](./leetcode_python/Linked_list/linked-list-components.py)  | _O(m + n)_ | _O(m)_ | Medium || OK* 

data/to_review.txt

@@ -1,8 +1,10 @@
+2025-02-15 -> ['369']
 2025-02-14 -> ['370']
 2025-02-13 -> ['815,871,593,1109']
 2025-02-07 -> ['560,523']
 2025-02-01 -> ['304,853,325']
 2025-01-26 -> ['370(todo)']
+2025-01-25 -> ['369']
 2025-01-24 -> ['370', '34,767']
 2025-01-23 -> ['815,871,593,1109']
 2025-01-20 -> ['722,380']
@@ -11,20 +13,21 @@
 2025-01-16 -> ['776,31']
 2025-01-15 -> ['004(todo),34(todo),162(todo),275(todo)']
 2025-01-14 -> ['986(todo),1229(todo),1868(todo),80(todo),209(todo),283(todo),360(todo),713(todo),532(todo),611(todo)']
+2025-01-12 -> ['369']
 2025-01-11 -> ['370', '304,853,325', '394']
 2025-01-10 -> ['815,871,593,1109', '833,950']
 2025-01-05 -> ['370(todo)']
-2025-01-04 -> ['560,523', '53,210,207']
+2025-01-04 -> ['369', '560,523', '53,210,207']
 2025-01-03 -> ['370', '34,767', '444']
 2025-01-02 -> ['815,871,593,1109', '1188,130,855(again)']
-2024-12-30 -> ['722,380']
+2024-12-30 -> ['369', '722,380']
 2024-12-29 -> ['370', '304,853,325', '33,81']
 2024-12-28 -> ['815,871,593,1109', '900']
-2024-12-27 -> ['560,523', '253', '26,27', '802,1197,26']
+2024-12-27 -> ['369', '560,523', '253', '26,27', '802,1197,26']
 2024-12-26 -> ['370', '776,31']
-2024-12-25 -> ['815,871,593,1109', '004(todo),34(todo),162(todo),275(todo)']
-2024-12-24 -> ['370', '986(todo),1229(todo),1868(todo),80(todo),209(todo),283(todo),360(todo),713(todo),532(todo),611(todo)']
-2024-12-23 -> ['370', '815,871,593,1109', '370(todo)']
+2024-12-25 -> ['369', '815,871,593,1109', '004(todo),34(todo),162(todo),275(todo)']
+2024-12-24 -> ['369', '370', '986(todo),1229(todo),1868(todo),80(todo),209(todo),283(todo),360(todo),713(todo),532(todo),611(todo)']
+2024-12-23 -> ['369', '370', '815,871,593,1109', '370(todo)']
 2024-12-22 -> ['370', '815,871,593,1109', '560,523']
 2024-12-21 -> ['815,871,593,1109', '304,853,325', '34,767', '394', '855,846']
 2024-12-20 -> ['833,950', '932']

leetcode_java/src/main/java/LeetCodeJava/LinkedList/PlusOneLinkedList.java

@@ -31,12 +31,61 @@ public class PlusOneLinkedList {
    */
 
   // V0
+  // TODO : implement
 //  public ListNode plusOne(ListNode head) {
 //  }
 
+
   // V1
-  // https://leetcode.ca/2016-12-03-369-Plus-One-Linked-List/
+  // IDEA : LINKED LIST OP (gpt)
+  /**
+   *  Step 1) reverse linked list
+   *  Step 2) plus 1, bring `carry` to next digit if curSum > 9, ... repeat for all nodes
+   *  Step 3) reverse linked list again
+   */
   public ListNode plusOne_1(ListNode head) {
+    if (head == null) return new ListNode(1); // Handle edge case
+
+    // Reverse the linked list
+    head = reverseList(head);
+
+    // Add one to the reversed list
+    ListNode current = head;
+    int carry = 1; // Start with adding one
+
+    while (current != null && carry > 0) {
+      int sum = current.val + carry;
+      current.val = sum % 10; // Update the current node value
+      carry = sum / 10; // Calculate carry for the next node
+      if (current.next == null && carry > 0) {
+        current.next = new ListNode(carry); // Add a new node for carry
+        carry = 0; // No more carry after this
+      }
+      current = current.next;
+    }
+
+    // Reverse the list back to original order
+    return reverseList(head);
+  }
+
+  // Utility to reverse a linked list
+  private ListNode reverseList(ListNode head) {
+    ListNode prev = null;
+    ListNode current = head;
+
+    while (current != null) {
+      ListNode next = current.next; // Save the next node
+      current.next = prev; // Reverse the link
+      prev = current; // Move prev forward
+      current = next; // Move current forward
+    }
+
+    return prev;
+  }
+
+  // V2
+  // https://leetcode.ca/2016-12-03-369-Plus-One-Linked-List/
+  public ListNode plusOne_2(ListNode head) {
     ListNode dummy = new ListNode(0, head);
     ListNode target = dummy;
     while (head != null) {
@@ -54,5 +103,5 @@ public ListNode plusOne_1(ListNode head) {
     return dummy.val == 1 ? dummy : dummy.next;
   }
 
-  // V2
+  // V3
 }