Create Linked List Frequency.java

varunu28 · web-flow · commit 8c7400fb11c6 · 2024-03-08T06:34:57.000-08:00
diff --git a/Medium/Linked List Frequency.java b/Medium/Linked List Frequency.java
@@ -0,0 +1,25 @@
+/**
+ * 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 frequenciesOfElements(ListNode head) {
+        Map<Integer, Integer> map = new HashMap<>();
+        for (ListNode curr = head; curr != null; curr = curr.next) {
+            map.put(curr.val, map.getOrDefault(curr.val, 0) + 1);
+        }
+        ListNode dummy = new ListNode(-1);
+        ListNode curr = dummy;
+        for (Integer key : map.keySet()) {
+            curr.next = new ListNode(map.get(key));
+            curr = curr.next;
+        }
+        return dummy.next;
+    }
+}
