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Runtime: 4 ms, faster than 46.79% of C++ online submissions for Print Binary Tree. 可以看出，矩阵宽度是所有节点的和，长度是树高+1。然后就是二分，但要注意边界值。 阅读全文
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On a 2 dimensional grid with R rows and C columns, we start at (r0, c0) facing east. Here, the north-west corner of the grid is at the first row and c 阅读全文
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Given a binary tree, we install cameras on the nodes of the tree. Each camera at a node can monitor its parent, itself, and its immediate children. Ca 阅读全文
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Return all non-negative integers of length N such that the absolute difference between every two consecutive digits is K. Note that every number in th 阅读全文
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A binary tree is univalued if every node in the tree has the same value. Return true if and only if the given tree is univalued. 太简单了，签到题。 阅读全文
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Given a wordlist, we want to implement a spellchecker that converts a query word into a correct word. For a given query word, the spell checker handle 阅读全文