class Solution {
public:
    int findMaxLength(vector<int>& nums) {
        for(auto& num:nums)
            if(num==0)
                num=-1;
        unordered_map<int,int> m;
        m[0]=-1;
        int sum=0;
        int result=0;
        for(int i=0;i<nums.size();++i)
        {
            sum+=nums[i];
            if(m.find(sum)!=m.end())
                result=max(result,i-m[sum]);
            else
                m[sum]=i;
        }
        return result;
    }
};