Find the length of the largest subarray with 0 sum | GeeksForGeeks

Subscribe to my newsletter and never miss my upcoming articles

Given an array of integers, find the length of the longest sub-array with sum equals to 0.

Examples :

Input: arr[] = {15, -2, 2, -8, 1, 7, 10, 23}; Output: 5 Explanation: The longest sub-array with elements summing up-to 0 is {-2, 2, -8, 1, 7}

Input: arr[] = {1, 2, 3} Output: 0 Explanation:There is no subarray with 0 sum

Input: arr[] = {1, 0, 3} Output: 1 Explanation: The longest sub-array with elements summing up-to 0 is {0}

Approach: Prefix Sum

// A Java program to find maximum length subarray with 0 sum 

class MaxLenZeroSumSub { 

    // 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 (arr[i] == 0 && max_len == 0) 
                max_len = 1; 

            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 method 
    public static void main(String arg[]) 
    { 
        int arr[] = { 15, -2, 2, -8, 1, 7, 10, 23 }; 
        System.out.println("Length of the longest 0 sum subarray is "
                        + maxLen(arr)); 
    } 
}

No Comments Yet