Fullstack Developer

There is a robot on an m x n grid. The robot is initially located at the top-left corner (i.e., grid[0][0]). The robot tries to move to the bottom-right corner (i.e., grid[m - 1][n - 1]). The robot can only move either down or right at any point in time.Given the two integers m and n, return the number of possible unique paths that the robot can take to reach the bottom-right corner.for example: Input: m = 3, n = 7Output: 28

What do you understand about the Singleton design pattern?
What is the Factory Method design pattern?
What is concurrent hashmap and how it is implemented in Java.?
Difference between concurrent and synchronized collection.

You are visiting a farm that has a single row of fruit trees arranged from left to right. The trees are represented by an integer array of fruits where fruits[i] is the type of fruit the ith tree produces.You want to collect as much fruit as possible. However, the owner has some strict rules that you must follow:You only have two baskets, and each basket can only hold a single type of fruit. There is no limit on the amount of fruit each basket can hold.Starting from any tree of your choice, you must pick exactly one fruit from every tree (including the start tree) while moving to the right. The picked fruits must fit in one of your baskets.Once you reach a tree with fruit that cannot fit in your baskets, you must stop.Given the integer array of fruits, return the maximum number of fruits you can pick.

There are n gas stations along a circular route, where the amount of gas at the ith station is gas[i].You have a car with an unlimited gas tank and it costs cost[i] of gas to travel from the ith station to its next (i + 1)th station. You begin the journey with an empty tank at one of the gas stations.Given two integer arrays gas and cost, return the starting gas station's index if you can travel around the circuit once in the clockwise direction, otherwise return -1. If there exists a solution, it is guaranteed to be unique.