• Subject: n-queens -> save the solutions
• From: Maxime Chupin <notezik@...>
• Date: Mon, 1 Aug 2011 09:09:00 +0100

Hi !

I am playing with the n-queen problem to learn Lua. I want to save all the solution in a list (solutions) but it does not work and I do not understand why. Here my very simple code with which my problem is more understandable.

local N=6

local solutions={}

function NQueen(q,r)
if r==N+1 then
-- debug
char=""
for e=1,N do
char=char..q[e].." "
end
print(char.."\n") -- THIS PRINT THE RIGHT ARRAYS
-- end debug
solutions[#solutions+1]=q
else
for j=1,N do
valid=true
for i=1,(r-1) do
if ((q[i]==j or math.abs(q[i]-j)==math.abs(r-
i)) and r>1) then
valid=false
end
end
if valid then
q[r]=j
NQueen(q,r+1)
end
end
end
end

Dq={}
for i=1,N do
Dq[i]=0
end

NQueen(Dq,1)
print(#solutions.." solutions found") -- RIGHT NUMBER OF SOLUTIONS
local drawSol=solutions[2]
local char=""
for f=1,N do
char=char..drawSol[f].." "
end
print(char) -- THIS PRINT A WRONG ARRAY

--
Maxime Chupin
http://mc.notezik.com