<p>Given a binary array <code>nums</code>, return <em>the maximum length of a contiguous subarray with an equal number of </em><code>0</code><em> and </em><code>1</code>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> nums = [0,1]
<strong>Output:</strong> 2
<strong>Explanation:</strong> [0, 1] is the longest contiguous subarray with an equal number of 0 and 1.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> nums = [0,1,0]
<strong>Output:</strong> 2
<strong>Explanation:</strong> [0, 1] (or [1, 0]) is a longest contiguous subarray with equal number of 0 and 1.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= nums.length &lt;= 10<sup>5</sup></code></li>
	<li><code>nums[i]</code> is either <code>0</code> or <code>1</code>.</li>
</ul>

class Solution {
public:
    bool isValid(vector<int>& integral_nums, int k) {
        for(int i = k;i < integral_nums.size();i++) {
            if (integral_nums[i] - integral_nums[i-k] == k/2) {
                return true;
            }
        }
        return false;
    }

    int findMaxLength(vector<int>& nums) {
        if (nums.size() <= 1) {
            return 0;
        }
        
        vector<int> integral_nums(1, 0);
        int integral = 0;
        for(int i = 0;i < nums.size();i++) {
            integral += nums[i];
            integral_nums.push_back(integral);
        }
        
        int max_len = nums.size();
        if (max_len % 2 == 1) max_len--;

        while(max_len >= 2) {
            if (isValid(integral_nums, max_len)) {
                return max_len;
            }
            max_len -= 2;
        }

        return max_len;
    }
};
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