Two Sum

Box Stacking - Dynamic Programming

What happens when you enter a URL in the browser? - UI Edition

1. browser checks cache; if requested object is in cache and is fresh, skip to #9
2. browser asks OS for server's IP address
3. OS makes a DNS lookup and replies the IP address to the browser. Each DNS can forward to other DNS if it doesn’t have the data, till it reaches the root DNS (which will have the ip address)
4. browser opens a TCP connection to server (this step is much more complex with HTTPS) at port 80.
5. In case of HTTPs, it also creates a SSL connection (refer to stamp’s book)
6. browser sends the HTTP request through TCP connection
7. browser receives HTTP response and may close the TCP connection, or reuse it for another request
8. browser checks if the response is a redirect or a conditional response (3xx result status codes), authorization request (401), error (4xx and 5xx), etc.; these are handled differently from normal responses (2xx)
9. if cacheable, response is stored in cache
10. browser decodes response (e.g. if it's gzipped)
11. browser determines what to do with response (e.g. is it a HTML page, is it an image, is it a sound clip?)
12. browser renders response, or offers a download dialog for unrecognized types

Length of the longest substring

React lifecycle methods and the order in which they are called

String to Leet

Lessons Learnt:

mapper = {'a': 0};

if(mapper['a']) ---> is false

0 || undefined ---> is undefined

undefined || 0 ---> is 0

Create a line on a graph given 2 coordinates that define the line

CSS Box Sizing

 box-sizing: 'content-box' => width = width(content), does not include padding, border or margins -> default behaviour

box-sinzing: 'border-box' => width = width(content) + padding + border, does not include margins

Binary Heap properties

 A Binary Heap is a Binary Tree with following properties.

1) It’s a complete tree (All levels are completely filled except possibly the last level and the last level has all keys as left as possible). This property of Binary Heap makes them suitable to be stored in an array.

2) A Binary Heap is either Min Heap or Max Heap. In a Min Binary Heap, the key at root must be minimum among all keys present in Binary Heap. The same property must be recursively true for all nodes in Binary Tree. Max Binary Heap is similar to MinHeap.

• Arr[(i-1)/2]	Returns the parent node
  Arr[(2*i)+1]	Returns the left child node
  Arr[(2*i)+2]	Returns the right child node

Arr[(n/2) .... (n-1)] => will contain the leaf nodes, if n is the length of the array or total number of nodes.

The traversal method use to achieve Array representation is Level Order


Source: geeks for geeks

Powers of 2 to remember for scalability questions

 

O(log N)

O(N)

O(N log N)

O(N^2)

O(2^N)

O(N!)

Source: Cracking the coding interview

Binary Tree - DFS Preorder (Stacks)

Binary Tree - DFS PostOrder (Recursion)

Binary Tree - DFS PreOrder (Recursive)

Binary Tree - DFS Inorder Traversal (Recursion)