C++ || 99% faster || Simple DFS
```\nclass FindElements {\npublic:\n    vector mapper;\n    FindElements(TreeNode root) {\n        mapper.resize(1000005,false);\n        filterThis(root,0);\n 
```\nclass FindElements {\npublic:\n    vector<bool> mapper;\n    FindElements(TreeNode* root) {\n        mapper.resize(1000005,false);\n        filterThis(root,0);\n    }\n    void filterThis(TreeNode* root, int x) {\n        if(!root) return;\n        if(x<=1000001) {\n            mapper[x] = true; \n            filterThis(root->left, 2*x+1);\n            filterThis(root->right,2*x+2);\n        }\n    }\n    bool find(int target) {\n        return mapper[target];\n    }\n};
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