摘要：
Given an array w of positive integers, where w[i] describes the weight of index i, write a function pickIndex which randomly picks an index in proport 阅读全文
摘要：
Design a data structure that supports all following operations in average O(1) time. Example: Solution1: HashMap + ArrayList 1. use an ArrayList toget 阅读全文
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Given an unsorted array of integers, find the length of longest increasing subsequence. Example: Input: [10,9,2,5,3,7,101,18] Output: 4 Explanation: T 阅读全文
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S and T are strings composed of lowercase letters. In S, no letter occurs more than once. S was sorted in some custom order previously. We want to per 阅读全文
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Given a 2D matrix matrix, find the sum of the elements inside the rectangle defined by its upper left corner (row1, col1) and lower right corner (row2 阅读全文