Problem Statement in English

You are given a 0-indexed integer array nums. A subarray of nums is called balanced if the number of even integers in the subarray is equal to the number of odd integers in the subarray.

Return the length of the longest balanced subarray in nums. If there is no balanced subarray, return 0.

Approach

Judging by the constraints, we can easily get away with a brute force approach.

We can iterate through all the subarrays and check if they are balanced or not. If they are balanced, we can update our result.

And we’re done!

Solution in Python


class Solution:
    def longestBalanced(self, nums: List[int]) -> int:
        N = len(nums)
        res = 0

        for i in range(N):
            evens = set()
            odds = set()
            for j in range(i, N):
                n = nums[j]

                if n % 2:
                    odds.add(n)
                else:
                    evens.add(n)

                if len(evens) == len(odds):
                    res = max(res, j - i + 1)

        return res

Complexity

  • Time: $O(n^2)$
    Since we are iterating through all the subarrays.

  • Space: $O(n)$
    Since we are storing the even and odd numbers in sets.

And we are done.