implement FreqStack, a class which simulates the operation of a stack-like data structure.FreqStack has two functions:push(int x), which pushes an integer x onto the stack.pop(), which removes and returns the most frequent element in the stack.If there is a tie for most frequent element, the element closest to the top of the stack is removed and returned.

Given two integers dividend and divisor, divide two integers without using multiplication, division, and mod operator. Return the quotient after dividing dividend by divisor. The integer division should truncate toward zero, which means losing its fractional part. For example, truncate(8.345) = 8 and truncate(-2.7335) = -2.

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 operations on an initially empty stack.

Given an integer array nums, you need to find one continuous subarray that if you only sort this subarray in ascending order, then the whole array will be sorted in ascending order. Return the shortest such subarray and output its length.

Given a balanced parentheses string S, compute the score of the string based on the following rule: () has score 1 AB has score A + B, where A and B are balanced parentheses strings. (A) has score 2 * A, where A is a balanced parentheses string.

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 to right. Integers in each column are sorted in ascending from top to bottom.

Given a string and a string dictionary, find the longest string in the dictionary that can be formed by deleting some characters of the given string. If there are more than one possible results, return the longest word with the smallest lexicographical order. If there is no possible result, return the empty string

Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M.Given a roman numeral, convert it to an integer.

A linked list of length n is given such that each node contains an additional random pointer, which could point to any node in the list, or null.Construct a deep copy of ...

Given the root of a Binary Search Tree (BST), convert it to a Greater Tree such that every key of the original BST is changed to the original key plus sum of all keys greater than the original key in BST.