renew letsencrypt certs

./letsencrypt-auto renew

no module named interface -> http://stackoverflow.com/questions/38170100/letsencrypt-importerror-no-module-named-interface-on-amazon-linux-while-renewin

React.js fundamentals

Babel,webpack, ES6 => ES5

JS

functional programming -> map,filter,reduce

execution context -> call,bind,apply

ES6 new features

template strings

default arguments, variable arguments
arrow functions

lexical scoping for vars but dynamic scoping for this

but lexical scoping for this with arrow functions

destructuring => arrays and objects

react export,import similar to destructuring 
ES6 classes are similar to other OOP classes, but use prototyping in background

ssh-add linux Could not open a connection to your authentication agent.

eval `ssh-agent -s`

Burn subtitles to mp4 with handbrake

https://handbrake.fr

Android app to record audio/video without showing on screen

http://softwarerecs.stackexchange.com/questions/35123/android-app-to-record-audio-video-without-showing-on-screen?newsletter=1&nlcode=573107%7c9664

https://play.google.com/store/apps/details?id=com.jwork.spycamera.free3&hl=en

vob to mp4 converter windows

http://www.freemake.com/

huffman encoding java

import java.util.Comparator;

import java.util.PriorityQueue;

public class HuffMan {

public static void main(String[] args) {

PriorityQueue<Node1> q = new PriorityQueue<Node1>(new Comparator<Node1>() {

       public int compare(Node1 n1, Node1 n2) {

        return n1.freq.compareTo(n2.freq);

       }  

});

q.add(new Node1('a',2));

q.add(new Node1('b',2));

q.add(new Node1('c',3));

q.add(new Node1('d',3));

q.add(new Node1('e',5));

q.add(new Node1('f',6));

q.add(new Node1('g',7));

while(q.size()>1) {

Node1 n1 = q.poll();

Node1 n2 = q.poll();

Node1 n3 = new Node1(' ',n1.freq+n2.freq);

n3.l = n1;

n3.r = n2;

q.add(n3);

}

dfs(q.peek(),"");

print(q.peek());

}

private static void print(Node1 root) {

if(root.l == null && root.r == null) System.out.println(root.val+" "+root.freq+" "+root.code);

else {

if(root.l != null) print(root.l);

if(root.r != null) print(root.r);

}

}

private static void dfs(Node1 root,String prefix) {

if(root.l == null && root.r == null) root.code = prefix;

else {

if(root.l != null) dfs(root.l,prefix+"0");

if(root.r != null) dfs(root.r,prefix+"1");

}

}

}

class Node1 {

Node1 l;

Node1 r;

char val;

Integer freq;

String code;

public Node1(char val,int freq) {

l = r = null;

this.val = val;

this.freq = freq;

}

}