haocs

tmux shortcuts & cheatsheet

start new:

tmux

start new with session name:

tmux new -s myname

haocs

def binary_left(seq, target):
    l, r = 0, len(seq) - 1
    while l < r:
        mid = (l + r) // 2 # always choose the left half
        # if seq[mid] == target:
        #     r = mid
        if seq[mid] >= target:
            r = mid
 else:

haocs

def isDAG(G):
    # status: 1 discover 2 visited
    def has_cycle(G, status, node):
        if status[node] == 2:
            return False
        status[node] = 1
        neighbors = G[node]
        for neighbor in neighbors:
 if status[neighbor] == 1:

haocs

// Allow CORS for client side JS tests
app.use(function(req, res, next) {
  res.header("Access-Control-Allow-Origin", '*');
  res.header("Access-Control-Allow-Methods", 'HEAD,GET,PUT,POST,DELETE,PATCH,OPTIONS');
  // Allow all custom headers in reqeusts
  res.header("Access-Control-Allow-Headers", req.headers['access-control-request-headers']);
  // Specify headers
  //res.header('Access-Control-Allow-Headers', 'Content-Type, Authorization, Content-Length, X-Requested-With, x-ms-client-request-id');
  
  // intercept OPTIONS method

haocs

Keybase proof

I hereby claim:

• I am haocs on github.
• I am haocs (https://keybase.io/haocs) on keybase.
• I have a public key whose fingerprint is 4D6B F6A5 B482 44A8 2752 D189 978F 38F6 82A1 2F91

To claim this, I am signing this object:

haocs

var createFilter = function(i) {
    return {
      before: function(req) {
           return new Promise(function(resolve, reject) {
              setTimeout(function() {
                  console.log('[before hook] ' + i);
                  resolve(req);
              }, 500);
          });
      },

haocs

#System Design Interview Cheatsheet

Picking the right architecture = Picking the right battles + Managing trade-offs

##Basic Steps

1. Clarify and agree on the scope of the system

• User cases (description of sequences of events that, taken together, lead to a system doing something useful)
  • Who is going to use it?
  • How are they going to use it?

haocs

import random
import time
import unittest

__all__=['Cache']

_current_time_ms = lambda: int(round(time.time() * 1000))


"""

haocs

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns             
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns  =  20 µs
SSD random read ........................ 150,000 ns  = 150 µs

Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs

haocs

class RPN():
    _input_priority = {
        '*': 5,
        '/': 5,
        '+': 3,
        '-': 3,
        '(': 7,
        }
    _instack_priority = {
        '*': 6,