Challenge: Find the least positive missing number

swkidd — Thu, 21 May 2020 08:17:20 +0000

Find the least positive number missing from a list in linear time with constant extra space

ex:

[1,2,3,4] -> 5

[-1,0,1] -> 2

[-20,3,10,1] -> 2

One solution uses linear time and linear extra space. Then there's an extra spicy solution that uses linear time and constant space.

Quick list / feed scraping in the dev console

swkidd — Sun, 03 May 2020 05:01:27 +0000

// function to create array of elements from an xpath
let xeval = (s, each = e => e) => { 
  const iter = document.evaluate(s, document, null, XPathResult.ANY_TYPE, null );
  const elems = []
  while(elem = iter.iterateNext()) {
    elems.push(each(elem))
  }
  return elems
}

I was recently helping someone scrape app reviews and came across this tip. This will work to scrape any list / feed of elements.

The Problem

A lot of sites generate class names on page load, so you can't always use class names / id's to pull page data. The solution is to use XPATH. I was surprised by how easy this is!

Scroll down the page a bit and choose an element you want to scrape
Inspect the element and copy it's XPath

right click element in dev window -> copy -> XPath / full XPath

it will look like:
'.../div/div[10]/div/div[2]/div[1]/div[1]/span'
by deleting '[10]' all like elements will be selected
use the XPath to select the page elements

And that's it!

Here's the code

DEV Community: swkidd

Challenge: Find the least positive missing number

Quick list / feed scraping in the dev console

The Problem