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问题：
"(){}[]"   =>  True
"([{}])"   =>  True
"(}"       =>  False
"[(])"     =>  False
"[({})](]" =>  False
基本思想：在算法中设置一个栈，每读入一个括号，若是右括号，则或者与栈顶匹配的左括号相互消解，或者是不合法的情况；若是左括号，则直接压入栈中。
若括号匹配，在算法的开始和结束时，栈都应该是空的。

defmodule Challenge do

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Prepare Postgres for phoenix

Pre-Reqs

Brew Package Manager

In your command-line run the following commands:

1. brew doctor
2. brew update

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1. Begin with scaffolding a create-react-app, then update your package.json build script (replace DIR_TO_PHX_APP with the path to your phoenix app)

"build": "react-scripts build && rm -rf DIR_TO_PHX_APP/priv/static/build && mv build DIR_TO_PHX_APP/priv/static/build",

This will move your prod build files to DIR_TO_PHX_APP/priv/static/build on build

2. Run yarn build

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https://ryanstutorials.net/bash-scripting-tutorial/bash-if-statements.php

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#A plug to get cookies from conn
defmodule AuthorizedPlug do
    import Plug.Conn
    import Phoenix.Controller

    def init(options) do
        options
    end

    def call(conn, name) do

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Phoenix Nodes

First I created 3 droplets on digital ocean with 4-cores and 8GB of RAM. Login as root to each and run:

sysctl -w fs.file-max=12000500
sysctl -w fs.nr_open=20000500
ulimit -n 4000000
sysctl -w net.ipv4.tcp_mem='10000000 10000000 10000000'

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#start psql
psql postgres 

# list all databases
\l

#connect the db
\c db_name

#list all tables

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Common Options

-#, --progress-bar Make curl display a simple progress bar instead of the more informational standard meter.

-b, --cookie <name=data> Supply cookie with request. If no =, then specifies the cookie file to use (see -c).

-c, --cookie-jar <file name> File to save response cookies to.