82. Remove Duplicates from Sorted List II

/**
 * 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 static int lenLL(ListNode head){
        int len = 0;
        ListNode curr = head;
        while(curr != null){
            len++;
            curr = curr.next;
        }
        return len;
    }

    
    public static ListNode deleteDuplicates(ListNode head) {
        
        ListNode curr = head;
        int lengthOfLL = lenLL(head);
        int[] numFrequency = new int[lengthOfLL];
        int pos = 0;
        while (curr != null) {
            int count = 0;
            ListNode ptr2 = head;
            while (ptr2 != null) {
                if (curr.val == ptr2.val) {
                    ptr2 = ptr2.next;
                    count++;
                }
                else{
                ptr2 = ptr2.next;
                continue;
                }
            }
           curr = curr.next;
            numFrequency[pos] = count;
            pos++;
            
        }
        
        // for (int i = 0; i < numFrequency.length; i++) {
        //     System.out.print(numFrequency[i] + " ");
        // }
        // System.out.println();

        ListNode curr2 = head;
        int pos2 = 0;
        ListNode dummy = new ListNode();
        ListNode d = dummy;
        while(curr2 != null){
            if(numFrequency[pos2] == 1){
                ListNode temp = new ListNode(curr2.val);
                d.next = temp;
                d = d.next;
                d.next = null;
                curr2 = curr2.next;
                pos2++;
            }
            else{
            curr2 = curr2.next;
            pos2++;
            continue;
            }
            
        }
        return dummy.next;
    }
        }