local grid = {} -- grid of the cucumbers
for line in io.lines("25.txt") do
    local row = {}
    for char in line:gmatch(".") do
        table.insert(row, char)
    end
    table.insert(grid, row)
end

local gridCopy = {} -- copy of the grid to store the movements to be done
for i = 1, #grid do
    local rowCopy = {}
    for j = 1, #grid[1] do
        table.insert(rowCopy, ".")
    end
    table.insert(gridCopy, rowCopy)
end

local canMove = {} -- grid of booleans to see if we can move
for i = 1, #grid do
    local boolRow = {}
    for j = 1, #grid[1] do
        table.insert(boolRow, false)
    end
    table.insert(canMove, boolRow)
end

for n = 1, math.huge do
    local movCount = 0 -- count of movements done on a step
    for y = 1, #grid do -- check for ">" movements
        for x = 1, #grid[1] do
            if grid[y][x] == ">" and grid[y][x+1] then
                if grid[y][x+1] == "." then
                    canMove[y][x] = true
                    gridCopy[y][x+1] = ">"
                    movCount = movCount + 1
                end
            elseif grid[y][x] == ">" and grid[y][1] == "." then
                canMove[y][x] = true
                gridCopy[y][1] = ">"
                movCount = movCount + 1
            end
        end
    end
    for y = 1, #grid do -- move them
        for x = 1, #grid[1] do
            if canMove[y][x] then
                grid[y][x] = "."
            end
            if gridCopy[y][x] == ">" then
                grid[y][x] = ">"
            end
        end
    end
    for y = 1, #gridCopy do -- clear both other tables
        for x = 1, #gridCopy[1] do
            gridCopy[y][x] = "."
        end
    end
    for y = 1, #canMove do
        for x = 1, #canMove[1] do
            canMove[y][x] = false
        end
    end
    for y = 1, #grid do -- check for "v" movements
        for x = 1, #grid[1] do
            if grid[y][x] == "v" and grid[y+1] then
                if grid[y+1][x] == "." then
                    canMove[y][x] = true
                    gridCopy[y+1][x] = "v"
                    movCount = movCount + 1
                end
            elseif grid[y][x] == "v" and grid[1][x] == "." then
                canMove[y][x] = true
                gridCopy[1][x] = "v"
                movCount = movCount + 1
            end
        end
    end
    for y = 1, #grid do -- move them
        for x = 1, #grid[1] do
            if canMove[y][x] then
                grid[y][x] = "."
            end
            if gridCopy[y][x] == "v" then
                grid[y][x] = "v"
            end
        end
    end
    if movCount == 0 then -- if nothing has moved, break and print the solution
        print("They can't move after " .. n .. " steps")
        break
    end
    for y = 1, #gridCopy do -- clear both other tables for next iteration
        for x = 1, #gridCopy[1] do
            gridCopy[y][x] = "."
        end
    end
    for y = 1, #canMove do
        for x = 1, #canMove[1] do
            canMove[y][x] = false
        end
    end
end