sudokuCheck

/*
    This is a sudoku board checker program that I wrote after seeing the question
    being asked at a Google interview somewhere.

    Date: 110510, Tue 10 May 2011 10:11:32 AM IST
*/

// to check that the elements are indeed <=9 and >=1
int check1to9(int board[9][9]) {
    int i, j;
    for (i=0; i<9; ++i)
        for (j=0; j<9; ++j)
            if (board[i][j]<=0 || board[i][j]>9)
                return 0;
    return 1;
}

// cheeck each row and each column for presence of all 9 digits
int checkRowColumn(int board[9][9]) {
    int i, j;
    int testRow[10], testCol[10];
    int sumRow, sumCol;

    for (i=0; i<9; ++i) {
        for (j=1; j<=9; ++j)
            testRow[j] = testCol[j] = 0;
        for (j=0; j<9; ++j) {
            testRow[board[i][j]]=1;
            testCol[board[j][i]]=1;
        }
        sumRow = sumCol = 0;
        for (j=1; j<=9; ++j) {
            sumRow += testRow[j];
            sumCol += testCol[j];
        }
        if (sumRow!=9 || sumCol!=9)
            return 0;
    }
    return 1;
}

// check each box for presence of all 9 digits
int checkBox(int board[9][9]) {
    int i, j, sum;
    int test[10];
    for (i=0; i<9; i+=3)
        for (j=0; j<9; j+=3) {
            for (k=1; k<=9; ++k)
                test[k]=0;
            for (r=i; r<i+3; ++r)
                for (c=j; c<j+3; ++c)
                    test[board[r][c]]=1;
            sum=0;
            for (k=1; k<=9; ++k)
                sum += test[k];
            if (sum!=9)
                return 0;
        }
    return 1;
}

// final function
int sudokuCheck (int board[9][9]) {
    if (check1to9(board) && checkRowColumn(board) && checkBox(board))
        return 1;
    return 0;
}