多言数穷，不如守中。十语九中，未必称奇；一语未中，愆尤骈集。

The string is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility)And then read line by line: Write the code that will take a string and make this conversion given a

Given a string , return the longest palindromic substring in .Example 1:Example 2:Constraints:

Given two sorted arrays and of size and respectively, return the median of the two sorted arrays.The overall run time complexity should be .Example 1:Example 2:Constraints:

Given a string `s`, find the length of the **longest** **substring** without repeating characters.

You are given two **non-empty** linked lists representing two non-negative integers. The digits are stored in **reverse order**, and each of their nodes contains a single digit. Add the two numbers and return the sum as a linked list.

Write a program to solve a Sudoku puzzle by filling the empty cells.A sudoku solution must satisfy all of the following rules:The character indicates empty cells.Example 1:Constraints:

Given an integer , return *an array of length such that for each (), is the number of ’s in the binary representation of *.Example 1:Example 2:Constraints:Follow up:

Given an integer , return if it is a power of two. Otherwise, return .An integer is a power of two, if there exists an integer such that .Example 1:Example 2:Example 3:Constraints:Follow up: Could you solve it without loops/recursion?

Write a function that takes the binary representation of a positive integer and returns the number of set bits it has (also known as the Hamming weight).Example 1:Output: 3Explanation:The input binary string 1011 has a total of three set bits.Example 2:Out

Given a non-negative integer , return the square root of rounded down to the nearest integer. The returned integer should be non-negative as well.You must not use any built-in exponent function or operator.Example 1:Example 2:Constraints:

The n-queens puzzle is the problem of placing queens on an chessboard such that no two queens attack each other.Given an integer , return all distinct solutions to the n-queens puzzle. You may return the answer in any order.Each solution contains a disti

Given `n` pairs of parentheses, write a function to *generate all combinations of well-formed parentheses*.

0, 10^5]

Given the of a binary tree, return its maximum depth.A binary tree’s maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.Example 1:Example 2:Constraints:

Given the of a binary tree, return the level order traversal of its nodes’ values. (i.e., from left to right, level by level).Example 1:Example 2:Example 3:Constraints:

You are given an integer array where is the price of a given stock on the day.On each day, you may decide to buy and/or sell the stock. You can only hold at most one share of the stock at any time. However, you can buy it then immediately sell it on the

Given an array of size , return the majority element.The majority element is the element that appears more than times. You may assume that the majority element always exists in the array.Example 1:Example 2:Constraints:Follow-up: Could you solve the pr

qpq。

qpq。

Implement pow(x, n), which calculates raised to the power (i.e., ).Example 1:Example 2:Example 3:Constraints:

You are given two integer arrays and , sorted in non-decreasing order, and two integers and , representing the number of elements in and respectively.Merge and into a single array sorted in non-decreasing order.The final sorted array should not be re

n1or2。

Given the of a binary tree, determine if it is a valid binary search tree (BST).A valid BST is defined as follows:Example 1:Example 2:Constraints:

You are given an array of integers , there is a sliding window of size which is moving from the very left of the array to the very right. You can only see the numbers in the window. Each time the sliding window moves right by one position.Return the max

Given , the head of a linked list, determine if the linked list has a cycle in it.There is a cycle in a linked list if there is some node in the list that can be reached again by continuously following the pointer. Internally, is used to denote the index

0, 100]

Given the of a singly linked list, reverse the list, and return the reversed list.Example 1:Example 2:Example 3:Constraints:Follow up: A linked list can be reversed either iteratively or recursively. Could you implement both?

Given two strings and , return if is an anagram of , and otherwise.An Anagram is a word or phrase formed by rearranging the letters of a different word or phrase, typically using all the original letters exactly once.Example 1:Example 2:Constraints:F

Design a data structure that follows the constraints of a Least Recently Used (LRU) cache.Implement the class:The functions and must each run in average time complexity.Example 1:Constraints:

Design a class to find the largest element in a stream. Note that it is the largest element in the sorted order, not the distinct element.Implement class:Example 1:Constraints:

Implement a first in first out (FIFO) queue using only two stacks. The implemented queue should support all the functions of a normal queue (, , , and ).Implement the class:* Pushes element x to the back of the queue.* Removes the element from the front

Implement a last-in-first-out (LIFO) stack using only two queues. The implemented stack should support all the functions of a normal stack (, , , and ).Implement the class:Notes:Example 1:Constraints:Follow-up: Can you implement the stack using only one

Given a string containing just the characters , , , , and , determine if the input string is valid.An input string is valid if:Example 1:Example 2:Example 3:Constraints:* * consists of parentheses only .

【代码】【LeetCode 0151】【字符串】反转字符串中的单词。

【代码】【LeetCode 0028】【字符串】实现strStr。

【代码】【LeetCode 0125】【双指针】有效回文。

【代码】【LeetCode 0167】【数组】两数之和(3) 数据结构设计。

【代码】【LeetCode 0167】【数组】两数之和(2)

Given an array of integers and an integer , return indices of the two numbers such that they add up to .You may assume that each input would have exactly one solution, and you may not use the same element twice.You can return the answer in any order.Examp

【LeetCode 0026】【数组】 删除有序数组中的重复项数组。