Amazon

Amazon 4-for-3 deals

Posted July 25th, 2008 by Mgccl
in

Amazon 4-for-3 deal:
Buy 4 item and have the one with the least price free. 4-for-3 items are under $10.
I believe if I buy 4n books, then it will be made into a 4n-for-3n deal that's not in writing, where n items with the least price is free. I did not test it yet, hope someone try that for me. Maxium saving is 25%, not bad.

How to maximize the amount of saving, suppose there is no such thing as shipping fee(If you are in your Amazon prime trial period).

1. Assume one have to buy n items.
2. If n is divisible by 4, the best strategy is to sort the items by price, forms a series of prices a_i, where a_i\le a_{i+1}. This also forms set B.(uhh.. this set allows repetition of elements...)
3. Buy a vector of them each time <a_{4i+1}, a_{4i+2}, a_{4i+3}, a_{4i+4}> for 0\le i\le \frac{n}{4}-1, which will maximize saving.
Proof: The total amount of money paid for this method is
\sum _{i=1}^{n} a_i - \sum _{i=0}^{\frac{n}{4}-1} a_{4i+1}
Make each of the number removed into a set, S
Each time find one element for S, the 4 element of B is removed.
A non-rigorous proof
Create n blocks out of 4n elements in B, name it b_1,b_2,b_3.....b_n
S is set containing the minimal for each b_n.
we can see a_1 has to be part of S, and b_1.
suppose a_2 is not in b_1, but in b_k,
and a_i is the smallest number in b_1 other than a_i.
If one switch a_2 with a_i, we can find all the smallest number in b_k is larger than a_2. All the rest blocks doesn't change at all.
Which shows that a_2 must be in the same block with a_1 to allow the sum of S be maximized.
use the same reasoning for a_3 and a_4.
and use the same reasoning for all blocks.
we get the original way have to be the best way.
If the count of elements in B is not divisible by 4, the best way is still the same, group items of 4 from most expensive to least expensive, remain a few least expensive ones in one group, buy each group separately.

This can be extended to any n-for-n-1 deals and should be able to extend to any n-for-k deals, where k lesser than n.

An amazon wishlist widget

Posted June 5th, 2007 by Mgccl
in

The project page will show you the source.
The idea is originally from JunkIWant, Amazon Adgent and few other amazon widgets in Widgetbox Because non of those are open source(I might be wrong due to only 10 minute of research), this widget will be a cool amazon rotation widget with source codes and without all those annoying copy right stuff and Widgetbox's platform.

This is something I and Simon is working on. Currently it reads a amazon wishlist, and show the result in a rotating fashion. When mouse move over it, the rotation stops until the mouse moves out.
Simon did the Javascript section, I did the PHP part. It requires PHP5(I think).
I will explain throughly tomorrow. Here is the demo

Todo:
1. back and forward buttons
2. User can chose what to show and what not to show
3. Fix the strange elongation problem.
4. Extend it so it shows content related ads like Amazon Adgent
5. If possible, make it jQuery based
6. Drupal plugin!
7. Add to facebook!

Syndicate content
Honey Pot that kill bots