随笔分类 - Google
摘要：You have 4 cards each containing a number from 1 to 9. You need to judge whether they could operated through *, /, +, -, (, ) to get the value of 24.
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摘要：Given a non-empty list of words, return the k most frequent elements. Your answer should be sorted by frequency from highest to lowest. If two words h
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摘要：Given a string, find the first non-repeating character in it and return it's index. If it doesn't exist, return -1. Examples: Note: You may assume the
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摘要：Given preorder and inorder traversal of a tree, construct the binary tree. Note:You may assume that duplicates do not exist in the tree. For example,
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摘要：Given a binary tree, find its maximum depth. The maximum depth is the number of nodes along the longest path from the root node down to the farthest l
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摘要：Given a binary tree, return the zigzag level order traversal of its nodes' values. (ie, from left to right, then right to left for the next level and
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摘要：TinyURL is a URL shortening service where you enter a URL such as https://leetcode.com/problems/design-tinyurl and it returns a short URL such as http
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摘要：Given a sorted array, two integers k and x, find the k closest elements to x in the array. The result should also be sorted in ascending order. If the
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摘要：Basic Calculator I Implement a basic calculator to evaluate a simple expression string. The expression string may contain open ( and closing parenthes
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摘要：Given two binary trees and imagine that when you put one of them to cover the other, some nodes of the two trees are overlapped while the others are n
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摘要：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
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摘要：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
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摘要：Path Sum I Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the g
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摘要：Given a complete binary tree, count the number of nodes. Definition of a complete binary tree from Wikipedia:In a complete binary tree every level, ex
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摘要：Determine whether an integer is a palindrome. Do this without extra space. 分析：把一个数倒过来，然后看两个数是否相同。 Reverse digits of an integer. Example1: x = 123, ret
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摘要：Suppose we abstract our file system by a string in the following manner: The string "dir\n\tsubdir1\n\tsubdir2\n\t\tfile.ext" represents: dir subdir1
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摘要：Given two strings s and t, determine if they are isomorphic. Two strings are isomorphic if the characters in s can be replaced to get t. All occurrenc
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摘要：Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center). For example, this binary tree [1,2,2,3,4,4,3] is symmet
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摘要：Given an array of strings, group anagrams together. For example, given: ["eat", "tea", "tan", "ate", "nat", "bat"], Return:
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摘要：Clone an undirected graph. Each node in the graph contains a label and a list of its neighbors. OJ's undirected graph serialization: Nodes are labeled
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