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Invert a binary tree. Example: Input: Output: code 阅读全文
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Given a non-negative integer c, your task is to decide whether there're two integers a and b such that a2 + b2 = c. Example 1: Example 2: 题意： 给定非负整数c， 阅读全文
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A group of two or more people wants to meet and minimize the total travel distance. You are given a 2D grid of values 0 or 1, where each 1 marks the h 阅读全文
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Write a program that outputs the string representation of numbers from 1 to n. But for multiples of three it should output “Fizz” instead of the numbe 阅读全文
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Given a linked list, return the node where the cycle begins. If there is no cycle, return null. To represent a cycle in the given linked list, we use 阅读全文
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You are given two integer arrays nums1 and nums2 sorted in ascending order and an integer k. Define a pair (u,v) which consists of one element from th 阅读全文
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Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand. (i.e., [0,1,2,4,5,6,7] might become [4,5,6,7,0,1,2]). F 阅读全文
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Given two sequences pushed and popped with distinct values, return true if and only if this could have been the result of a sequence of push and pop o 阅读全文
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如图 阅读全文
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Given a 2D board and a word, find if the word exists in the grid. The word can be constructed from letters of sequentially adjacent cell, where "adjac 阅读全文
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You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed, the only constraint stopping yo 阅读全文
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You are given coins of different denominations and a total amount of money amount. Write a function to compute the fewest number of coins that you nee 阅读全文
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There are G people in a gang, and a list of various crimes they could commit. The i-th crime generates a profit[i] and requires group[i] gang members 阅读全文
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如题 阅读全文
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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 阅读全文
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Find the minimum length word from a given dictionary words, which has all the letters from the string licensePlate. Such a word is said to complete th 阅读全文
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Given a string, sort it in decreasing order based on the frequency of characters. Example 1: Example 2: Example 3: 题意： 按频率将字母排序 Solution1: HashMap cod 阅读全文
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Design a HashMap without using any built-in hash table libraries. To be specific, your design should include these functions: put(key, value) : Insert 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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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 阅读全文