[C++] Find the Difference of Two Arrays using unordered_set
Thinking Process:\nAdd all elements of both array in a set.\nThen iterate through both array and using find() method, if the element is not found in other set, 
**Thinking Process:**\nAdd all elements of both array in a set.\nThen iterate through both array and using find() method, if the element is not found in other set, add it to the answer.\nDo this for both the arrays and return the answer.\n\n```\nclass Solution {\npublic:\n    vector<vector<int>> findDifference(vector<int>& nums1, vector<int>& nums2) {\n\t//unordered_set is implemented using a hash table where keys are hashed into indices of a hash table\n\t// all operations take O(1) on average\n        unordered_set<int> n1;\n        unordered_set<int> n2;\n        for(int i=0;i<nums1.size();i++)\n            n1.insert(nums1[i]);\n        \n        for(int i=0;i<nums2.size();i++)\n            n2.insert(nums2[i]);\n        \n        vector<int> ans1;\n\t\tvector<vector<int>> ans;\n        for(int x:n1)\n        {\n            if(n2.find(x)==n2.end())\n                ans1.push_back(x);\n        }\n\t\tans.push_back(ans1);\n\t\tans1.clear();\n        for(int x:n2)\n        {\n            if(n1.find(x)==n1.end())\n                ans1.push_back(x);\n        }\n        ans.push_back(ans1);\n        return ans;\n    }\n};\n```\n**Time Complexity: O(n)**\n where n is max(n1,n2), for iterating through both arrays and adding elements to set.\n \n Edit: using a single array for holding the answer.
['C', 'Ordered Set']