Sudoku Solver in C

I had this code lying around, so I figured I would submit this as my first attempt at a weekend-challenge. I would prefer if reviews contained suggestions on how to improve the algorithm, but all suggestions are acceptable.

```
#include

int isAvailable(int puzzle[][9], int row, int col, int num)
{
int rowStart = (row/3) * 3;
int colStart = (col/3) * 3;
int i, j;

for(i=0; i<9; ++i)
{
if (puzzle[row][i] == num) return 0;
if (puzzle[i][col] == num) return 0;
if (puzzle[rowStart + (i%3)][colStart + (i/3)] == num) return 0;
}
return 1;
}

int fillSudoku(int puzzle[][9], int row, int col)
{
int i;
if(row<9 && col<9)
{
if(puzzle[row][col] != 0)
{
if((col+1)<9) return fillSudoku(puzzle, row, col+1);
else if((row+1)<9) return fillSudoku(puzzle, row+1, 0);
else return 1;
}
else
{
for(i=0; i<9; ++i)
{
if(isAvailable(puzzle, row, col, i+1))
{
puzzle[row][col] = i+1;
if((col+1)<9)
{
if(fillSudoku(puzzle, row, col +1)) return 1;
else puzzle[row][col] = 0;
}
else if((row+1)<9)
{
if(fillSudoku(puzzle, row+1, 0)) return 1;
else puzzle[row][col] = 0;
}
else return 1;
}
}
}
return 0;
}
else return 1;
}

int main()
{
int i, j;
int puzzle[9][9]={{0, 0, 0, 0, 0, 0, 0, 9, 0},
{1, 9, 0, 4, 7, 0, 6, 0, 8},
{0, 5, 2, 8, 1, 9, 4, 0, 7},
{2, 0, 0, 0, 4, 8, 0, 0, 0},
{0, 0, 9, 0, 0, 0, 5, 0, 0},
{0, 0, 0, 7, 5, 0, 0, 0, 9},
{9, 0, 7, 3, 6, 4, 1, 8, 0},

Your solution is short and sweet. Hopefully my answer will be too since rolfl covered most of what I saw. :)

-
Perhaps solveSudoku will better convey the fact that it's solving the puzzle. fillSudoku sounds like a function that fills in the initial positions from a file or string or something.

-
You could shorten the "is the cell is filled" check by dropping the != 0 for maximum C-ness:

if(puzzle[row][col])

-
You are duplicating the code that advances the cell indices in fillSudoku: once if the cell comes in already filled and again when you place the next guess. You can drop the latter and simply pass in the same cell indices since you're setting the cell's value first.

if(isAvailable(puzzle, row, col, i+1))
{
    puzzle[row][col] = i+1;

    if(fillSudoku(puzzle, row, col) return 1;
    else puzzle[row][col] = 0;
}

StackExchange Code Review Q#37430, answer score: 19