Largest subarray with 0 sum.java

// code start

// { Driver Code Starts
import java.util.*;

class MaxLenZeroSumSub
{

    // Returns length of the maximum length subarray with 0 sum

    // Drive method
    public static void main(String arg[])
    {
        Scanner sc = new Scanner(System.in);
        int T = sc.nextInt();
        while (T > 0)
        {
            int n = sc.nextInt();
            int arr[] = new int[n];
            for (int i = 0; i < n; i++)
                arr[i] = sc.nextInt();

            GfG g = new GfG();
            System.out.println(g.maxLen(arr, n));
            T--;
        }
    }
}// } Driver Code Ends


class GfG
{
    int maxLen(int arr[], int n)
    {
        // Your code here
       HashMap<Integer,Integer> hm = new HashMap<>();
       int res=0,sum=0;
       hm.put(0,-1);
       for(int i=0;i<n;i++)
       {
           sum+=arr[i];
           if(!hm.containsKey(sum))
           {
               hm.put(sum,i);
           }
           else
           {
               int idx=hm.get(sum);
               res=Math.max(res,i-idx);
           }
       }
       return res;
    }
}

// code end