原文链接: https://leetcode-cn.com/problems/combination-sum-iii 英文原文Find all valid combinations of k numbers that sum up to n such that the following conditions are true: Only numbers 1 through 9 are used. Each number is used at most once. Return a list o…

原文链接: https://leetcode-cn.com/problems/contains-duplicate 英文原文Given an integer array nums, return true if any value appears at least twice in the array, and return false if every element is distinct. Example 1: Input: nums = [1,2,3,1] Output: true Ex…

原文链接: https://leetcode-cn.com/problems/the-skyline-problem 英文原文A city's skyline is the outer contour of the silhouette formed by all the buildings in that city when viewed from a distance. Given the locations and heights of all the buildings, return …

原文链接: https://leetcode-cn.com/problems/contains-duplicate-ii 英文原文Given an integer array nums and an integer k, return true if there are two distinct indices i and j in the array such that nums[i] == nums[j] and abs(i - j) <= k. Example 1: Input: nums…

原文链接: https://leetcode-cn.com/problems/contains-duplicate-iii 英文原文Given an integer array nums and two integers k and t, return true if there are two distinct indices i and j in the array such that abs(nums[i] - nums[j]) <= t and abs(i - j) <= k. Exam…

原文链接: https://leetcode-cn.com/problems/maximal-square 英文原文Given an m x n binary matrix filled with 0's and 1's, find the largest square containing only 1's and return its area. Example 1: Input: matrix = [["1","0","1","0","0"],["1","0","1","1","1"],[…

原文链接: https://leetcode-cn.com/problems/count-complete-tree-nodes 英文原文Given the root of a complete binary tree, return the number of the nodes in the tree. According to Wikipedia, every level, except possibly the last, is completely filled in a comple…

原文链接: https://leetcode-cn.com/problems/rectangle-area 英文原文Given the coordinates of two rectilinear rectangles in a 2D plane, return the total area covered by the two rectangles. The first rectangle is defined by its bottom-left corner (ax1, ay1) and …

原文链接: https://leetcode-cn.com/problems/basic-calculator 英文原文Given a string s representing a valid expression, implement a basic calculator to evaluate it, and return the result of the evaluation. Note: You are not allowed to use any built-in function…

原文链接: https://leetcode-cn.com/problems/invert-binary-tree 英文原文Given the root of a binary tree, invert the tree, and return its root. Example 1: Input: root = [4,2,7,1,3,6,9] Output: [4,7,2,9,6,3,1] Example 2: Input: root = [2,1,3] Output: [2,3,1] Exa…

原文链接: https://leetcode-cn.com/problems/basic-calculator-ii 英文原文Given a string s which represents an expression, evaluate this expression and return its value. The integer division should truncate toward zero. You may assume that the given expression …

原文链接: https://leetcode-cn.com/problems/summary-ranges 英文原文You are given a sorted unique integer array nums. Return the smallest sorted list of ranges that cover all the numbers in the array exactly. That is, each element of nums is covered by exactly…

原文链接: https://leetcode-cn.com/problems/majority-element-ii 英文原文Given an integer array of size n, find all elements that appear more than &lfloor; n/3 &rfloor; times. Example 1: Input: nums = [3,2,3] Output: [3] Example 2: Input: nums = [1] Output: [1…

原文链接: https://leetcode-cn.com/problems/kth-smallest-element-in-a-bst 英文原文Given the root of a binary search tree, and an integer k, return the kth smallest value (1-indexed) of all the values of the nodes in the tree. Example 1: Input: root = [3,1,4,n…

原文链接: https://leetcode-cn.com/problems/power-of-two 英文原文Given an integer n, return true if it is a power of two. Otherwise, return false. An integer n is a power of two, if there exists an integer x such that n == 2x. Example 1: Input: n = 1 Output: …

原文链接: https://leetcode-cn.com/problems/number-of-digit-one 英文原文Given an integer n, count the total number of digit 1 appearing in all non-negative integers less than or equal to n. Example 1: Input: n = 13 Output: 6 Example 2: Input: n = 0 Output: 0 …

原文链接: https://leetcode-cn.com/problems/implement-queue-using-stacks 英文原文Implement a first in first out (FIFO) queue using only two stacks. The implemented queue should support all the functions of a normal queue (push, peek, pop, and empty). Implemen…

原文链接: https://leetcode-cn.com/problems/palindrome-linked-list 英文原文Given the head of a singly linked list, return true if it is a palindrome. Example 1: Input: head = [1,2,2,1] Output: true Example 2: Input: head = [1,2] Output: false Constraints: The…

原文链接: https://leetcode-cn.com/problems/lowest-common-ancestor-of-a-binary-search-tree 英文原文Given a binary search tree (BST), find the lowest common ancestor (LCA) of two given nodes in the BST. According to the definition of LCA on Wikipedia: &ldquo;T…

原文链接: https://leetcode-cn.com/problems/delete-node-in-a-linked-list 英文原文Write a function to delete a node in a singly-linked list. You will not be given access to the head of the list, instead you will be given access to the node to be deleted direct…

原文链接: https://leetcode-cn.com/problems/product-of-array-except-self 英文原文Given an integer array nums, return an array answer such that answer[i] is equal to the product of all the elements of nums except nums[i]. The product of any prefix or suffix of…

原文链接: https://leetcode-cn.com/problems/sliding-window-maximum 英文原文You are given an array of integers nums, there is a sliding window of size k which is moving from the very left of the array to the very right. You can only see the k numbers in the wi…

原文链接: https://leetcode-cn.com/problems/different-ways-to-add-parentheses 英文原文Given a string expression of numbers and operators, return all possible results from computing all the different possible ways to group numbers and operators. You may return…

原文链接: https://leetcode-cn.com/problems/search-a-2d-matrix-ii 英文原文Write an efficient algorithm that searches for a target value in an m x n integer matrix. The matrix has the following properties: Integers in each row are sorted in ascending from left…

原文链接: https://leetcode-cn.com/problems/valid-anagram 英文原文Given two strings s and t, return true if t is an anagram of s, and false otherwise. Example 1: Input: s = "anagram", t = "nagaram" Output: true Example 2: Input: s = "rat", t = "car" Output: f…

原文链接: https://leetcode-cn.com/problems/binary-tree-paths 英文原文Given the root of a binary tree, return all root-to-leaf paths in any order. A leaf is a node with no children. Example 1: Input: root = [1,2,3,null,5] Output: ["1->2->5","1->3"] Example 2:…

原文链接: https://leetcode-cn.com/problems/single-number-iii 英文原文Given an integer array nums, in which exactly two elements appear only once and all the other elements appear exactly twice. Find the two elements that appear only once. You can return the …

原文链接: https://leetcode-cn.com/problems/trips-and-users 英文原文Table: Trips +-------------+----------+ | Column Name | Type | +-------------+----------+ | id | int | | client_id | int | | driver_id | int | | city_id | int | | status | enum | | request_at…

原文链接: https://leetcode-cn.com/problems/ugly-number 英文原文An ugly number is a positive integer whose prime factors are limited to 2, 3, and 5. Given an integer n, return true if n is an ugly number. Example 1: Input: n = 6 Output: true Explanation: 6 = …

原文链接: https://leetcode-cn.com/problems/ugly-number-ii 英文原文An ugly number is a positive integer whose prime factors are limited to 2, 3, and 5. Given an integer n, return the nth ugly number. Example 1: Input: n = 10 Output: 12 Explanation: [1, 2, 3, …