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Hi Maxime,

You need to story a copy of your "q" array, because it gets modified later.

local N=6

local solutions={}

function NQueen(q,r)
   if r==N+1 then
      -- debug
      char=""
      local qcopy = {}
      for e=1,N do
         char=char..q[e].." "
	 qcopy[e] = q[e]
      end
      print(char.."\n") -- THIS PRINT THE RIGHT ARRAYS
      -- end debug
      solutions[#solutions+1]=qcopy
   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


Thanks,
Dimiter "malkia" Stanev.


On 8/1/11 1:09 AM, Maxime Chupin wrote:

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