# Month: February 2021

## Max Points on a Line

Given n points on a 2D plane, find the maximum number of points that lie on the same straight line.

## Happy Number

In number theory, a happy number is a number which eventually reaches 1 when replaced by the sum of the square of each digit.

## Next Greater Element I

You are given two integer arrays nums1 and nums2 both of unique elements, where nums1 is a subset of nums2. Find all the next greater numbers for nums1’s elements in the corresponding places of nums2. The Next Greater Number of a number x in nums1 is the first greater number to its right in nums2. If it does not exist, return -1 for this number.

## Single Element in a Sorted Array

You are given a sorted array consisting of only integers where every element appears exactly twice, except for one element which appears exactly once. Find this single element that appears only once.

## Search a 2D Matrix II

Write an efficient algorithm that searches for a target value in an m x n integer matrix.

## Smallest Common Region

You are given some lists of regions where the first region of each list includes all other regions in that list. Naturally, if a region X contains another region Y then X is bigger than Y. Also by definition a region X contains itself.

## String to Integer (atoi)

Here we are going to write our own atoi() implementation in Java. Remember in Java you convert a string to an integer using the parseInt method of the Java Integer class. The parseInt method converts the String to an int, and throws a NumberFormatException if the string can’t be converted to an int type.

## How to sort HashMap in Java by Keys ?

How to sort HashMap in Java by Keys

## House Robber

You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed, the only constraint stopping you from robbing each of them is that adjacent houses have security system connected and it will automatically contact the police if two adjacent houses were broken into on the same night.

## Path with Maximum Gold

In a gold mine grid of size m * n, each cell in this mine has an integer representing the amount of gold in that cell, 0 if it is empty.