An integer interval [a, b] (for integers a < b) is a set of all consecutive integers …

题目： Given a binary tree, flatten it to a linked list in-place. For example, Given 1 / \ 2 5 / \ \ 3 4 6 The fl…

题目描述 Find the contiguous subarray within an array (containing at least one number) which has the largest produ…

1. 题目 You are climbing a stair case. It takes n steps to reach to the top. Each time you can either climb 1 or…

70. Climbing Stairs 题目 You are climbing a stair case. It takes n steps to reach to the top. Each time you can …

  Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity. &nbs…

  Write a SQL query to find all duplicate emails in a table named Person. +----+---------+ | Id | Email |…

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  Given a sequence of words, check whether it forms a valid word square. A sequence of words forms a vali…

Divide Two Integers Divide two integers without using multiplication, division and mod operator. If it is over…

3Sum Smaller Given an array of n integers nums and a target, find the number of index triplets i, j, k with 0 …

Restore IP Address Given a string containing only digits, restore it by returning all possible valid IP addres…