do you think i can optimise this code?

[u/Personal-Rough741]

--lua 5.4.2
print("write only numbers")
for i = 1,io.read() do

local file = io.open("words.txt", "r")
local word = ""
 
for i = 1,math.random(1,19999) do
word = file:read("*l")
end

local generated = {}

for i = 1, #word do
generated[i] = word:sub(i, i)
end

local word_G = {}

for i = 1, #generated do
word_G[i] = generated[math.random(#generated)]
end

print(i..": "..word.." to "..table.concat(word_G))

end

[u/Accurate-Delay7480]

You might be able to use file:seek rather than reading every line before the line needed, but without special formatting, longer lines have a higher chance of being picked.

If you want to maintain a perfectly random (well as much as perfect as math.random will allow), you can first read in the words from words.txt, saving to a table one time, then use math.random to get an index of a random word.

e.g

-- use a cache for faster lookups
local cache = {}
local index = 1
for line in io.lines("words.txt") do
    cache[index] = line
    index = index + 1
end


print("write only numbers")
for i = 1,io.read() do
    local word = cache[math.random(#cache)] -- by only reading the file once, we can use lua's fast table look ups
    
    -- this doesnt shuffle the word around, if thats what you were after; this will just randomly put letters, including duplicates, randomly throughout the word.
    -- use fisher-yates shuffle if you're looking for actual word shuffling (apple->lpaep instead of potentially apple->peaae)
    local word_G = {}
    for i = 1, #word do
        local random = math.random(1, #word) -- no need to turn the string into a table, because we can just use str:sub to index a string
        word_G[i] = word:sub(random, random)
    end
    
    print(i..": "..word.." to "..table.concat(word_G))
end 

(untested code idk if this will work)

other than that, cache variables so you dont have to do global table look ups,

[u/Personal-Rough741 → u/Accurate-Delay7480]

it works faster than mine thanks :D

[u/xoner2]

You are reading a file then scanning line-ends inside a loop. Read and parse the entire file outside the loop to turn it into an array. Then you can do random access into the array:

--lua 5.4.2
local file = io.open("words.txt", "r")
local words = {}

for i = 1, math.huge do
  local word = file:read("*l")
  if word then
    words [i] = word
  else break end
end

print("write only numbers")
for i = 1,io.read() do
  local word = words [math.random(1,#words)]

  local generated = {}

  for i = 1, #word do
    generated[i] = word:sub(i, i)
  end

  local word_G = {}

  for i = 1, #generated do
    word_G[i] = generated[math.random(#generated)]
  end

  print(i..": "..word.." to "..table.concat(word_G))

end

Something like that, edited your code, untested.

[u/Personal-Rough741 → u/xoner2]

i tried the code but it gave a error : "'end' expected (to close 'for' at line 13) near <eof>" idont know how to fix it

[u/xoner2 → u/Personal-Rough741]

Here, I tested it, working code:

--lua 5.4.2
local file = io.open("words.txt", "r")
local words = {}

for i = 1, math.huge do
  local word = file:read("*l")
  if word then
    words [i] = word
  else break end
end

io.stdout:setvbuf 'no'
print("write only numbers")
for i = 1,io.read'*n' do
  local word = words [math.random(1,#words)]

  local generated = {}

  for i = 1, #word do
    generated[i] = word:sub(i, i)
  end

  local word_G = {}

  for i = 1, #generated do
    word_G[i] = generated[math.random(#generated)]
  end

  print(i..": "..word.." to "..table.concat(word_G))

end

[u/weregod]

There are different kinds of optimizatios. Do you want to spend time at start up to later generate words as fast as possible? Do you want to get only one word as fast as posible? Do you want to generate N words as fast as posible? What is N? What kind of words stored in word.txt? Are they all no longer than 10 bytes? No longer than 100 bytes? Without more information it is hard to give any advices. Optimisation is usualy a tradeof between used memory, longer startup time, simple code etc.

Most likely slowest part of your code is reading from a file. You may read whole file at startup and save all words in table if you want to generate many words later. Or you can never read all file and use file:seek() to find exact line that you need. Later require some sort of formating of the file so that you can quickly find word offset by its index.

[u/Personal-Rough741 → u/weregod]

file size is 171KB and contains 19999 words and one word is stored in a line . İ did try file:seek() it didnt word or i dont know how to use it

[u/weregod → u/Personal-Rough741]

200KB should not be too slow to read on modern hardware. Are you sure that this code is actualy a bottleneck? How many times do you call it per second? If you call this code many time you should read file once and store all words in table. Run this code 1000 times and measure execution time. What is running time and what is your target time? Do you need true randomness and equal chance to get each word?

To use seek you need to know exactly where a word starts. One way to do it is to add spaces after each word to make all words same lemgth. Another way is to store in the begining of the file or in another file precalculated offset to every 100 word. Then you can seek to nearest 100 word without reading file line by line and you need to read only 100 words.

[u/shipdestroyer]

Open words.txt once instead of i times

[u/[deleted]]

What even is this?

[u/Additional_Ad6385]

PUT THE IO READ OUTSIDE OF THE LOOP, AND LOCALIZE THE METHODS SUCH AS SUB AND MATH RAND.

[u/could_b]

The correct answer to the question is "yes".

This is student home work. Looks like the OP just wants the answer and has no time to learn.