Create Double a Number Represented as a Linked List.java

varunu28 · web-flow · commit 1f3c0a22ddaa · 2024-05-06T19:45:36.000-07:00
diff --git a/Medium/Double a Number Represented as a Linked List.java b/Medium/Double a Number Represented as a Linked List.java
@@ -0,0 +1,40 @@
+/**
+ * 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; }
+ * }
+ */
+class Solution {
+    public ListNode doubleIt(ListNode head) {
+        ListNode rev = reverse(head);
+        ListNode curr = rev;
+        int carry = 0;
+        while (curr != null) {
+            int val = curr.val * 2 + carry;
+            carry = val / 10;
+            curr.val = val % 10;
+            if (curr.next == null && carry != 0) {
+                curr.next = new ListNode(carry);
+                break;
+            }
+            curr = curr.next;
+        }
+        return reverse(rev);
+    }
+
+    private ListNode reverse(ListNode curr) {
+        ListNode next = null;
+        ListNode prev = null;
+        while (curr != null) {
+            next = curr.next;
+            curr.next = prev;
+            prev = curr;
+            curr = next;
+        }
+        return prev;
+    }
+}
