alg-visualizer/8queens.lua

-- Show the solutions to the Eight Queens problem with visualization

love.window.setMode(800, 600)

local size = 64
local img = love.graphics.newImage('queen-black-64x64.png')

local function clear(x, y)
  if (x + y) % 2 == 1 then
    love.graphics.setColor(0, 0, 0)
  else
    love.graphics.setColor(255, 255, 255)
  end
  love.graphics.rectangle("fill", x*size, y*size, size, size)
  love.graphics.setColor(255, 255, 255)
end

love.graphics.translate(love.graphics.getWidth()/2 - size*4,
                        love.graphics.getHeight()/2 - size*4)

love.graphics.rectangle("fill", -2, -2, size*8+4, size*8+4)
for y = 0, 7 do
  for x = 0, 7 do
    clear(x, y)
  end
end

local abs = math.abs

for q0 = 0, 7 do
  love.graphics.draw(img, q0*size, 0*size)
  -- Force display
  pause(0)
  for q1 = 0, 7 do
    if q1 ~= q0 and abs(q1 - q0) ~= 1 then
      love.graphics.draw(img, q1*size, 1*size)
      pause(0)
      for q2 = 0, 7 do
        if q2 ~= q0 and q2 ~= q1 and abs(q2 - q0) ~= 2 and abs(q2 - q1) ~= 1 then
          love.graphics.draw(img, q2*size, 2*size)
          pause(0)
          for q3 = 0, 7 do
            if q3 ~= q0 and q3 ~= q1 and q3 ~= q2
               and abs(q3 - q0) ~= 3 and abs(q3 - q1) ~= 2 and abs(q3 - q2) ~= 1
            then
              love.graphics.draw(img, q3*size, 3*size)
              pause(0)
              for q4 = 0, 7 do
                if q4 ~= q0 and q4 ~= q1 and q4 ~= q2 and q4 ~= q3
                   and abs(q4 - q0) ~= 4 and abs(q4 - q1) ~= 3
                   and abs(q4 - q2) ~= 2 and abs(q4 - q3) ~= 1
                then
                  love.graphics.draw(img, q4*size, 4*size)
                  pause(0)
                  for q5 = 0, 7 do
                    if q5 ~= q0 and q5 ~= q1 and q5 ~= q2 and q5 ~= q3
                       and q5 ~= q4
                       and abs(q5 - q0) ~= 5 and abs(q5 - q1) ~= 4
                       and abs(q5 - q2) ~= 3 and abs(q5 - q3) ~= 2
                       and abs(q5 - q4) ~= 1
                    then
                      love.graphics.draw(img, q5*size, 5*size)
                      pause(0)
                      for q6 = 0, 7 do
                        if q6 ~= q0 and q6 ~= q1 and q6 ~= q2 and q6 ~= q3
                           and q6 ~= q4 and q6 ~= q5
                           and abs(q6 - q0) ~= 6 and abs(q6 - q1) ~= 5
                           and abs(q6 - q2) ~= 4 and abs(q6 - q3) ~= 3
                           and abs(q6 - q4) ~= 2 and abs(q6 - q5) ~= 1
                        then
                          love.graphics.draw(img, q6*size, 6*size)
                          pause(0)
                          for q7 = 0, 7 do
                            if q7 ~= q0 and q7 ~= q1 and q7 ~= q2 and q7 ~= q3
                               and q7 ~= q4 and q7 ~= q5 and q7 ~= q6
                               and abs(q7 - q0) ~= 7 and abs(q7 - q1) ~= 6
                               and abs(q7 - q2) ~= 5 and abs(q7 - q3) ~= 4
                               and abs(q7 - q4) ~= 3 and abs(q7 - q5) ~= 2
                               and abs(q7 - q6) ~= 1
                            then
                              love.graphics.draw(img, q7*size, 7*size)
                              print("--------")
                              print(string.rep(" ", q0) .. "Q")
                              print(string.rep(" ", q1) .. "Q")
                              print(string.rep(" ", q2) .. "Q")
                              print(string.rep(" ", q3) .. "Q")
                              print(string.rep(" ", q4) .. "Q")
                              print(string.rep(" ", q5) .. "Q")
                              print(string.rep(" ", q6) .. "Q")
                              print(string.rep(" ", q7) .. "Q")
                              pause(0.5)
                              clear(q7, 7)
                            end
                          end
                          clear(q6, 6)
                        end
                      end
                      clear(q5, 5)
                    end
                  end
                  clear(q4, 4)
                end
              end
              clear(q3, 3)
            end
          end
          clear(q2, 2)
        end
      end
      clear(q1, 1)
    end
  end
  clear(q0, 0)
end

quit()