[R-sig-finance] [offtopic] solving sudoku in R?

[Krishna Kumar]

As sudoku seems to be in fad this season how about a fast solver in R. ?
I wrote a little thingie that just does an exhaustive search and was 
wondering if this could be speeded up,
I am particularly interested in putting some intelligence in to it and 
any  speedups that could be done.

Currently doing,
 >  system.time(sudoku()) 
[1] 18.25  0.02 18.43    NA    NA

18 secs for the default puzzle.Also is there a way to count function 
evaluations in R (a-la-matlab flops)?.

 Suggestions welcome.


Best,
Kris

# ref: http://en.wikipedia.org/wiki/Sudoku
# Simple nobrains solver
# Krishna Kumar
# oMat is the original puzzle,bMat keeps a backup 
sudoku<-function(oMat=NULL,bMat=NULL)
{
if (length(oMat) < 1)
{ # use this sudoku if none is given
     oMat<-matrix(c(0, 1, 0 ,0 ,0 ,0, 0, 7, 0,
        3, 0, 2 ,1 ,0 ,9, 8, 0, 4,
        0 ,0, 0, 5, 0, 8, 0, 0, 0,
        6, 0, 0, 0, 9, 0, 0, 0, 2,
        0, 4, 0, 0, 0, 0, 0, 3, 0,
        8, 0, 0, 0, 3, 0, 0, 0, 7,
        0, 0, 0, 9, 0, 5, 0, 0, 0,
        2, 0, 4, 7, 0, 3, 9, 0, 1,
        0, 9, 0, 0, 0, 0, 0, 4, 0),9,9)
        print(oMat)
}
indx<-which(oMat==0,arr.ind=T) # where are the empty cells
if(length(indx) > 0) {
row.num<-indx[,1]
col.num<-indx[,2]
}
else {
    print("solution")
    return(oMat) #voila!
}
x<-row.num[1]
y<-col.num[1]
for (i in 1:9) # try 1 to 9
    { sub.y<-1+3*floor((y-1)/3) # find the submatrix 3x3 block for the 
current solution
        sub.x<-1+3*floor((x-1)/3)
    if (!( any(oMat[x,]==i) | any(oMat[,y]==i) | 
any((oMat[seq(sub.x,sub.x+2),seq(sub.y,sub.y+2)]==i)) )) { # if valid 
number
        work<-oMat
        work[x,y]<-i
        work<-Recall(oMat=work,bMat=oMat); # solve with this if we fail 
then we just return to the original matrix
        if (all(work))  {
            oMat<-work # voila!
            return(oMat) 
        }
   }
}
    return(bMat)
}

<cid:part1.01050202.07020505 at earthlink.net>