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Decode String (M) 题目 Given an encoded string, return its decoded string. The encoding rule is: k[encoded_string], where the encoded_string inside the 阅读全文
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Mirror Reflection (M) 题目 There is a special square room with mirrors on each of the four walls. Except for the southwest corner, there are receptors o 阅读全文
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Longest Mountain in Array (M) 题目 Let's call any (contiguous) subarray B (of A) a mountain if the following properties hold: B.length >= 3 There exists 阅读全文
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Range Sum of BST (E) 题目 Given the root node of a binary search tree, return the sum of values of all nodes with a value in the range [low, high]. Exam 阅读全文
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Poor Pigs (H) 题目 There are 1000 buckets, one and only one of them is poisonous, while the rest are filled with water. They all look identical. If a pi 阅读全文
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Populating Next Right Pointers in Each Node (M) 题目 You are given a perfect binary tree where all leaves are on the same level, and every parent has tw 阅读全文
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Valid Square (M) 题目 Given the coordinates of four points in 2D space, return whether the four points could construct a square. The coordinate (x,y) of 阅读全文
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Flipping an Image (E) 题目 Given a binary matrix A, we want to flip the image horizontally, then invert it, and return the resulting image. To flip an i 阅读全文
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Maximum Difference Between Node and Ancestor (M) 题目 Given the root of a binary tree, find the maximum value V for which there exist different nodes A 阅读全文
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Binary Tree Tilt (E) 题目 Given the root of a binary tree, return the sum of every tree node's tilt. The tilt of a tree node is the absolute difference 阅读全文