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Given a non negative integer number num. For every numbers i in the range 0 ≤ i ≤ num calculate the number of 1's in their binary representation and r 阅读全文
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Given N axis-aligned rectangles where N > 0, determine if they all together form an exact cover of a rectangular region. Each rectangle is represented 阅读全文
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Given a positive integer n, find the least number of perfect square numbers (for example, 1, 4, 9, 16, ...) which sum to n. For example, given n = 12, 阅读全文
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Given an integer n, return 1 - n in lexicographical order. For example, given 13, return: [1,10,11,12,13,2,3,4,5,6,7,8,9]. Please optimize your algori 阅读全文
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Median is the middle value in an ordered integer list. If the size of the list is even, there is no middle value. So the median is the mean of the two 阅读全文
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Given a 2D binary matrix filled with 0's and 1's, find the largest square containing only 1's and return its area. For example, given the following ma 阅读全文
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Given an integer n, count the total number of digit 1 appearing in all non-negative integers less than or equal to n. For example: Given n = 13, Retur 阅读全文
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Given an integer array with all positive numbers and no duplicates, find the number of possible combinations that add up to a positive integer target. 阅读全文
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Implement a basic calculator to evaluate a simple expression string. The expression string may contain open ( and closing parentheses ), the plus + or 阅读全文
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Given a string that contains only digits 0-9 and a target value, return all possibilities to add binary operators (not unary) +, -, or * between the d 阅读全文