Easiest Solution Using HashMap || O(n)
Intuition\n Describe your first thoughts on how to solve this problem. \n\n# Approach\n Describe your approach to solving the problem. \n\n# Complexity\n- Time 
# Intuition\n<!-- Describe your first thoughts on how to solve this problem. -->\n\n# Approach\n<!-- Describe your approach to solving the problem. -->\n\n# Complexity\n- Time complexity: O(N)\n<!-- Add your time complexity here, e.g. $$O(n)$$ -->\n\n- Space complexity: O(N)\n<!-- Add your space complexity here, e.g. $$O(n)$$ -->\n\n# Code\n```java []\nclass Solution {\n    public int minImpossibleOR(int[] nums) {\n        int num=1;\n        HashSet<Integer>set=new HashSet<>();\n\n        for(int i=0;i<nums.length;i++)set.add(nums[i]);\n\n\n        for(int i=0;i<nums.length;i++){\n           if(!set.contains(num))return num;\n           num=num*2;\n        }\n        return num;\n    }\n}\n```
['Java']