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Given a non-empty 2D array grid of 0's and 1's, an island is a group of 1's (representing land) connected 4-directionally (horizontal or vertical.) Yo 阅读全文
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Given a 2d grid map of '1's (land) and '0's (water), count the number of islands. An island is surrounded by water and is formed by connecting adjacen 阅读全文
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Given a positive integer, check whether it has alternating bits: namely, if two adjacent bits will always have different values. Example 1: Example 2: 阅读全文
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Given two strings s and t, determine if they are isomorphic. Two strings are isomorphic if the characters in s can be replaced to get t. All occurrenc 阅读全文
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Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum. F 阅读全文
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The count-and-say sequence is the sequence of integers with the first five terms as following: 1 is read off as "one 1" or 11.11 is read off as "two 1 阅读全文