1171. Remove zero sum consecutive nodes from linked list

//1171. Remove zero sum consecutive nodes from linked list

import java.util.HashMap;
import java.util.Map;

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 removeZeroSumSublists(ListNode head) {
    	
        Map<Integer, ListNode> map = new HashMap<>();
        ListNode dummy = new ListNode(0);
        dummy.next = head;
        int prefixSum = 0;
        map.put(prefixSum, dummy);

        while(head != null) {
            prefixSum += head.val;
            
            if(map.containsKey(prefixSum)) {
                ListNode start = map.get(prefixSum);
                ListNode curr = start;
                int sum = prefixSum;
                
                while(curr != head) {
                    curr = curr.next;
                    sum += curr.val;
                    
                    if(curr != head) {
                        map.remove(sum);
                    }
                }

                start.next = head.next;
            }

            else {
                map.put(prefixSum, head);
            }

            head = head.next;
        }

        return dummy.next;
    }
}