2D - Instantiate gameobjects in tiles from a .txt?

I'm trying to make a "semi random" dungeon generator in which diferent levels layout randomly get instantiate when you go through "portals". The poblem is that, say i want to make 1000 diferent level layouts and i need all of them to be lightweight. So, i think a good idea is to use .txt files which contains words and make a script read them and depending the word it reads in the first line and column, instantiate a gameobject in the first tile of my map and so on and so forth. The thing is i have no clue in how to achieve this, so if someone can help me or guide me somehow i'd be highly grateful. Also i want to create or use some empty .txt to save the previous levels which the player go through, so he can return to a previous level if he wants to. Thanks in advance!

Example
----
AAA-AA--P--AA-AAA
AA--------------------AA
A-----BB------BB-----A
-------B----------B-------
----------------------------
-------B----------B-------
A-----BB------BB-----A
AA--------------------AA
AAA-AA--P--AA-A A A
---
A = rock / B = tree / P = portal / blank space = nothing
( I know the example is no well made but it's for you to understand me )

 

you could use numbers instead of letters, break the string into single letters and cast the strings as int. then you can simply have a list with the according tiles and pull one depending via the int.

 

I did something like this for songs.

i used the first digit of each number for the octave and the second digit for the note.
songs came out like this:

1C

1C

1A

1C



1D

1D

1A

1D



...etc.

StreamReader(reading text)/StreamWriter(writing text)

https://support.unity3d.com/hc/en-u...ow-do-I-read-and-write-data-from-a-text-file-

 

Thanks. You both gave me an overall idea and looking cautiously the code i finally achieved it exactly the way i want it to be.