* ----------------------
* This class stores an indexed, two-dimensional array. The following code,
* for example, creates an identity matrix of size n, in which
* the elements are 1.0 along the main diagonal and 0.0 everywhere else:
*
*
* Grid<double> createIdentityMatrix(int n) {
* Grid<double> matrix(n, n);
* for (int i = 0; i < n; i++) {
* matrix[i][i] = 1.0;
* }
* return matrix;
* }
*
*/
template
class Grid {
public:
/* Forward reference */
class GridRow;
class ConstGridRow;
/*
* Constructor: Grid
* Usage: Grid grid;
* Grid grid(nRows, nCols);
* ------------------------------------------
* Initializes a new grid. The second form of the constructor is
* more common and creates a grid with the specified number of rows
* and columns. Each element of the grid is initialized to the
* default value for the type. The default constructor creates an
* empty grid for which the client must call resize to
* set the dimensions.
*/
Grid();
Grid(int nRows, int nCols);
/*
* Destructor: ~Grid
* -----------------
* Frees any heap storage associated with this grid.
*/
virtual ~Grid();
/*
* Method: numRows
* Usage: int nRows = grid.numRows();
* ----------------------------------
* Returns the number of rows in the grid.
*/
int numRows() const;
/*
* Method: numCols
* Usage: int nCols = grid.numCols();
* ----------------------------------
* Returns the number of columns in the grid.
*/
int numCols() const;
/*
* Method: resize
* Usage: grid.resize(nRows, nCols);
* ---------------------------------
* Reinitializes the grid to have the specified number of rows
* and columns. Any previous grid contents are discarded.
*/
void resize(int nRows, int nCols);
/*
* Method: inBounds
* Usage: if (grid.inBounds(row, col)) ...
* ---------------------------------------
* Returns true if the specified row and column position
* is inside the bounds of the grid.
*/
bool inBounds(int row, int col) const;
/*
* Method: get
* Usage: ValueType value = grid.get(row, col);
* --------------------------------------------
* Returns the element at the specified row/col
* position in this grid. This method signals an error if the
* row and col arguments are outside
* the grid boundaries.
*/
ValueType get(int row, int col);
const ValueType & get(int row, int col) const;
/*
* Method: set
* Usage: grid.set(row, col, value);
* ---------------------------------
* Replaces the element at the specified row/col
* location in this grid with a new value. This method signals an error
* if the row and col arguments are outside
* the grid boundaries.
*/
void set(int row, int col, ValueType value);
/*
* Operator: []
* Usage: grid[row][col]
* ----------------------
* Overloads [] to select elements from this grid.
* This extension enables the use of traditional array notation to
* get or set individual elements. This method signals an error if
* the row and col arguments are outside
* the grid boundaries.
*/
GridRow operator[](int row);
const ConstGridRow operator[](int row) const;
/*
* Method: toString
* Usage: string str = grid.toString();
* ------------------------------------
* Converts the grid to a printable string representation.
*/
std::string toString();
/*
* Method: mapAll
* Usage: grid.mapAll(fn);
* -----------------------
* Calls the specified function on each element of the grid. The
* elements are processed in row-major order, in which
* all the elements of row 0 are processed, followed by the elements
* in row 1, and so on.
*/
void mapAll(void (*fn)(ValueType value)) const;
void mapAll(void (*fn)(const ValueType & value)) const;
template
void mapAll(FunctorType fn) const;
/*
* Additional Grid operations
* --------------------------
* In addition to the methods listed in this interface, the Grid
* class supports the following operations:
*
* - Stream I/O using the << and >> operators
* - Deep copying for the copy constructor and assignment operator
* - Iteration using the range-based for statement and STL iterators
*
* The iteration forms process the grid in row-major order.
*/
/* Private section */
/**********************************************************************/
/* Note: Everything below this point in the file is logically part */
/* of the implementation and should not be of interest to clients. */
/**********************************************************************/
/*
* Implementation notes: Grid data structure
* -----------------------------------------
* The Grid is internally managed as a dynamic array of elements.
* The array itself is one-dimensional, the logical separation into
* rows and columns is done by arithmetic computation. The layout
* is in row-major order, which is to say that the entire first row
* is laid out contiguously, followed by the entire second row,
* and so on.
*/
/* Instance variables */
ValueType *elements; /* A dynamic array of the elements */
int nRows; /* The number of rows in the grid */
int nCols; /* The number of columns in the grid */
/* Private method prototypes */
void checkRange(int row, int col);
/*
* Hidden features
* ---------------
* The remainder of this file consists of the code required to
* support deep copying and iteration. Including these methods
* in the public interface would make that interface more
* difficult to understand for the average client.
*/
/*
* Deep copying support
* --------------------
* This copy constructor and operator= are defined to make a
* deep copy, making it possible to pass/return grids by value
* and assign from one grid to another. The entire contents of
* the grid, including all elements, are copied. Each grid
* element is copied from the original grid to the copy using
* assignment (operator=). Making copies is generally avoided
* because of the expense and thus, grids are typically passed
* by reference, however, when a copy is needed, these operations
* are supported.
*/
void deepCopy(const Grid & grid) {
int n = grid.nRows * grid.nCols;
elements = new ValueType[n];
for (int i = 0; i < n; i++) {
elements[i] = grid.elements[i];
}
nRows = grid.nRows;
nCols = grid.nCols;
}
public:
Grid & operator=(const Grid & src) {
if (this != &src) {
delete[] elements;
deepCopy(src);
}
return *this;
}
Grid(const Grid & src) {
deepCopy(src);
}
/*
* Iterator support
* ----------------
* The classes in the StanfordCPPLib collection implement input
* iterators so that they work symmetrically with respect to the
* corresponding STL classes.
*/
class iterator : public std::iterator {
public:
iterator(const Grid *gp, int index) {
this->gp = gp;
this->index = index;
}
iterator(const iterator & it) {
this->gp = it.gp;
this->index = it.index;
}
iterator & operator++() {
index++;
return *this;
}
iterator operator++(int) {
iterator copy(*this);
operator++();
return copy;
}
bool operator==(const iterator & rhs) {
return gp == rhs.gp && index == rhs.index;
}
bool operator!=(const iterator & rhs) {
return !(*this == rhs);
}
ValueType & operator*() {
return gp->elements[index];
}
ValueType *operator->() {
return &gp->elements[index];
}
private:
const Grid *gp;
int index;
};
iterator begin() const {
return iterator(this, 0);
}
iterator end() const {
return iterator(this, nRows * nCols);
}
/*
* Private class: Grid::GridRow
* -------------------------------------
* This section of the code defines a nested class within the Grid template
* that makes it possible to use traditional subscripting on Grid values.
*/
class GridRow {
public:
GridRow() {
/* Empty */
}
ValueType & operator[](int col) {
if (!gp->inBounds(row, col)) {
throw std::out_of_range("Grid index values out of range");
}
return gp->elements[(row * gp->nCols) + col];
}
ValueType operator[](int col) const {
if (!gp->inBounds(row, col)) {
throw std::out_of_range("Grid index values out of range");
}
return gp->elements[(row * gp->nCols) + col];
}
private:
GridRow(Grid *gridRef, int index) {
gp = gridRef;
row = index;
}
Grid *gp;
int row;
friend class Grid;
};
friend class ConstGridRow;
/*
* Private class: Grid::ConstGridRow
* -------------------------------------
* This section of the code defines a nested class within the Grid template
* that makes it possible to use traditional subscripting on Grid values for
* const versions of the Grid.
*/
class ConstGridRow {
public:
ConstGridRow() {
/* Empty */
}
ValueType operator[](int col) const {
if (!gp->inBounds(row, col)) {
throw std::out_of_range("Grid index values out of range");
}
return gp->elements[(row * gp->nCols) + col];
}
private:
ConstGridRow(const Grid *gridRef, int index) {
gp = gridRef;
row = index;
}
const Grid *gp;
int row;
friend class Grid;
};
friend class GridRow;
};
template
Grid::Grid() {
elements = NULL;
nRows = 0;
nCols = 0;
}
template
Grid::Grid(int nRows, int nCols) {
elements = NULL;
resize(nRows, nCols);
}
template
Grid::~Grid() {
if (elements != NULL) delete[] elements;
}
template
int Grid::numRows() const {
return nRows;
}
template
int Grid::numCols() const {
return nCols;
}
template
void Grid::resize(int nRows, int nCols) {
if (nRows < 0 || nCols < 0) {
throw std::invalid_argument("Attempt to resize grid to invalid size ("
+ std::to_string(nRows) + ", "
+ std::to_string(nCols) + ")");
}
if (elements != NULL) delete[] elements;
this->nRows = nRows;
this->nCols = nCols;
elements = new ValueType[nRows * nCols];
ValueType value = ValueType();
for (int i = 0; i < nRows * nCols; i++) {
elements[i] = value;
}
}
template
bool Grid::inBounds(int row, int col) const {
return row >= 0 && col >= 0 && row < nRows && col < nCols;
}
template
ValueType Grid::get(int row, int col) {
if (!inBounds(row, col)) throw std::out_of_range("get: Grid indices out of bounds");
return elements[(row * nCols) + col];
}
template
const ValueType & Grid::get(int row, int col) const {
if (!inBounds(row, col)) throw std::out_of_range("get: Grid indices out of bounds");
return elements[(row * nCols) + col];
}
template
void Grid::set(int row, int col, ValueType value) {
if (!inBounds(row, col)) throw std::out_of_range("set: Grid indices out of bounds");
elements[(row * nCols) + col] = value;
}
template
typename Grid::GridRow Grid::operator[](int row) {
return GridRow(this, row);
}
template
const typename Grid::ConstGridRow
Grid::operator[](int row) const {
return ConstGridRow(this, row);
}
template
void Grid::mapAll(void (*fn)(ValueType value)) const {
for (int i = 0; i < nRows; i++) {
for (int j = 0; j < nCols; j++) {
fn(get(i, j));
}
}
}
template
void Grid::mapAll(void (*fn)(const ValueType & value)) const {
for (int i = 0; i < nRows; i++) {
for (int j = 0; j < nCols; j++) {
fn(get(i, j));
}
}
}
template
template
void Grid::mapAll(FunctorType fn) const {
for (int i = 0; i < nRows; i++) {
for (int j = 0; j < nCols; j++) {
fn(get(i, j));
}
}
}
template
std::string Grid::toString() {
std::ostringstream os;
os << *this;
return os.str();
}
/*
* Implementation notes: << and >>
* -------------------------------
* The insertion and extraction operators use the template facilities in
* strlib.h to read and write generic values in a way that treats strings
* specially.
*/
template
std::ostream & operator<<(std::ostream & os, const Grid & grid) {
os << "{";
int nRows = grid.numRows();
int nCols = grid.numCols();
for (int i = 0; i < nRows; i++) {
if (i > 0) os << ", ";
os << "{";
for (int j = 0; j < nCols; j++) {
if (j > 0) os << ", ";
os << grid.get(i, j);
}
os << "}";
}
return os << "}";
}
template
std::istream & operator>>(std::istream & is, Grid & grid) {
std::vector> vec2d;
is >> vec2d;
int nRows = vec2d.size();
int nCols = (nRows == 0) ? 0 : vec2d[0].size();
grid.resize(nRows, nCols);
for (int i = 0; i < nRows; i++) {
for (int j = 0; j < nCols; j++) {
grid[i][j] = vec2d[i][j];
}
}
return is;
}
#endif