updated readme

Author: rupeshtiwari

README.md

@@ -1,11 +1,56 @@
+### What you should know before coding interview?
+
+Make sure you know Computer science [basic data structures](#data-structures-you-should-know). Also you should be aware of [fundamental algorithms](#fundamental-algorithms-you-should-know).
+
+### Ask Questions before coding
+
+Once they give you problem, don't start coding. Ask clarifying questions to make sure you understand the problem.
+
+Example: 
+- Will there be null/empty values on input?
+- Will all numbers in a binary tree integers?
+- 
+
+## What you should prepare?
+
+### Big O
+Learn Big O. Make sure you give what would be the `runtime complexity` and `memory complexity`.  
+
+`Iterative functions` take no extra memory and therefore, `memory complexity` is `constant` O(1). 
+`Recursive functions` take extra on the stack therefore, `memory complexity` is `lograrithmic` O(_logn_) 
+
+### Data Structures you should know
+
+- Hash Table
+- Linked List
+- Stack
+- Queue
+- Tree
+- Tries
+- Graphs
+- Vectors
+- Heaps
+
+### Fundamental algorithms you should know
+
+- Breadth-first search
+- Depth-first search
+- Merge sort
+
+## While solving problem
+
 ## Arrays
 
 ### Implement Binary Search on a Sorted Array
 
+Given a sorted array of integers, return the index of the given key. Return -1 if the key is not found.
+
 Run below script
 
 ```
 node .\src\arrays\binary-search.mjs
 ```
 
 ### Find Maximum in Sliding Window
+
+Given a large array of integers and a window of size w, find the current maximum value in the window as the window slides through the entire array.