LC - 525. Contiguous Array

class Solution {
public:
    int findMaxLength(vector<int>& nums) 
    {
        unordered_map<int,int> up; // record,idx
        int record = 0;
        up[0] = -1;
        int maxLen = 0;
        for(int i = 0; i < nums.size(); i++)
        {
            record = record + (nums[i] == 0 ? -1 : 1);
            if(up.count(record))
            {
                maxLen = max(maxLen, i - up[record]);
            }
            else
            {
                up[record] = i;
            }
        }
        return maxLen;
    }
};