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Given a 32-bit signed integer, reverse digits of an integer. Example 1: Example 2: Example 3: Note:Assume we are dealing with an environment which cou 阅读全文
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Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. An input string is valid if: No 阅读全文
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You are given a map in form of a two-dimensional integer grid where 1 represents land and 0 represents water. Grid cells are connected horizontally/ve 阅读全文
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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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Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M. For example, two is written as II in Roman numeral, just two one's 阅读全文
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Given a collection of numbers that might contain duplicates, return all possible unique permutations. Example: 思路 阅读全文