Comparing two documents - regex

Question

I have two very large lists. They both were originally in excel, but the larger one is a list of emails (about 160,000) of them with other information like their name and address etc. And the smaller one is a list of just 18,000 emails.
My question is what would be the easiest way to get rid of all 18,000 rows from the first document that contain the email addresses from the second?
I was thinking regex or maybe there is another application I can use? I have tried searching online but it seems like there isn't much specific to this. I also tried notepad++ but it freezes when I try to compare these large files.
-Thank You in Advance!!

Answer 1

Good question. One way I would tackle this is making a C++ program [you could extrapolate the idea to the language of your choice; You never mentioned which languages you were proficient in] that read each item of the smaller file into a vector of strings. First, of course, use Excel to save the files as CSV instead of XLS or XLSX, which will comma-separate the values so you can work with them easier. For the larger list, "Save As" a copy of just email addresses, deleting the other rows for now.
Then, you could open the larger list and use a nested loop to check if you should output to an output file. Something like:
bool foundMatch=false;
for(int y=0;y<LargeListVector.size();y++) {
for(int x=0;x<SmallListVector.size();x++) {
if(SmallListVector[x]==LargeListVector[y]) foundMatch=true;
}
if(!foundMatch) OutputVector.append(LargeListVector[y]);
foundMatch=false;
}
That might be partially pseudo-code, but do you get the idea?

Answer 2

So I read a forum post at : Here
=MATCH(B1,$A$1:$A$3,0)>0
Column B would be the large list, with the 160,000 inputs and column A was my list of things I needed to delete of 18,000.
I used this to match everything, and in a separate column pasted this formula. It would print out either an error or TRUE. If the data was in both columns it printed out true.
Then because I suck with excel, I threw this text into Notepad++ and searched for all lines that contained TRUE (match case, because in my case some of the data had the word true in it without caps.) I marked those lines, then under search, bookmarks, I removed all lines with bookmarks. Pasted that back into excel and voila.
I would like to thank you guys for helping and pointing me in the right direction :)