LengthOfLargestSubarrayWithZeroSum.java

// Java program for the above approach

import java.util.HashMap;

class LengthOfLargestSubarrayWithZeroSum {

    // Returns length of the maximum length
    // subarray with 0 sum
    static int maxLen(int arr[])
    {
        // Creates an empty hashMap hM
        HashMap<Integer, Integer> hM
                = new HashMap<Integer, Integer>();

        int sum = 0; // Initialize sum of elements
        int max_len = 0; // Initialize result

        // Traverse through the given array
        for (int i = 0; i < arr.length; i++) {
            // Add current element to sum
            sum += arr[i];

            if (sum == 0)
                max_len = i + 1;

            // Look this sum in hash table
            Integer prev_i = hM.get(sum);

            // If this sum is seen before, then update
            // max_len if required
            if (prev_i != null)
                max_len = Math.max(max_len, i - prev_i);
            else // Else put this sum in hash table
                hM.put(sum, i);
        }

        return max_len;
    }

    // Drive's code
    public static void main(String arg[])
    {
        int arr[] = { 15, -2, 2, -8, 1, 7, 10, 23 };

        // Function call
        System.out.println(
                "Length of the longest 0 sum subarray is "
                        + maxLen(arr));
    }
}