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Given a binary tree, determine if it is a valid binary search tree (BST). Assume a BST is defined as follows: * The left subtree of a node contains on 阅读全文
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Given a binary tree, you need to compute the length of the diameter of the tree. The diameter of a binary tree is the length of the longest path betwe 阅读全文
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Given a 2D binary matrix filled with 0's and 1's, find the largest rectangle containing only 1's and return its area. Example: Input: [ ["1","0","1"," 阅读全文
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Given n non-negative integers representing the histogram's bar height where the width of each bar is 1, find the area of largest rectangle in the hist 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. Example: Input: 1 0 1 0 0 1 0 1 1 1 阅读全文
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Given the head of a graph, return a deep copy (clone) of the graph. Each node in the graph contains a label (int) and a list (List[UndirectedGraphNode 阅读全文
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Given a list of non-overlapping axis-aligned rectangles rects, write a function pick which randomly and uniformily picks an integer point in the space 阅读全文
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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
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Invert a binary tree. Example: Input: 4 / \ 2 7 / \ / \ 1 3 6 9 Output: 4 / \ 7 2 / \ / \ 9 6 3 1 分治法 1.解决自己小三角，交换左右直接孩子。 2.递归，让自己的左右孩子也去做这件事情。 实现： /* 阅读全文
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Given a non-empty array of integers, return the k most frequent elements.Example 1:Input: nums = [1,1,1,2,2,3], k = 2Output: [1,2]Example 2:Input: num 阅读全文