RAII and dynamic memory in classes (part 2)
This lesson contains approximately 18 minutes of video content.
Our VectorInt implementation continued
Activity: Matrix resize
Graded Playground Autograder
Activity Prompt:
After
In this activity, you will finish a partially complete implementation of a MatrixInt class. The
MatrixInt should
allocate and deallocate a non-empty rows_ x cols_ array of ints in its
constructor and destructor,
respectively. You will also have to implement the Resize method, which will resize the non-empty 2D
array to the dimensions
specified. If the dimensions become smaller, values at the right and/or bottom edges will not be retained. If
the dimensions become bigger,
new values at the right and/or bottom will be initialized to zero.
Resize example:{{1, 2, 3},
{4, 5, 6},
{7, 8, 9}}
After
Resize(2,4) is called:{{1, 2, 3, 0},
{4, 5, 6, 0}}
| Function | Description |
|---|---|
MatrixInt(unsigned int rows, unsigned int cols) |
Constructor. Should dynamically allocate the non-empty 2D array of ints matrix_ with
rows rows and
cols cols, initialized to be all zeros.If rows or cols
are invalid, throw a
std::invalid_argument exception.
|
~MatrixInt() |
Destructor. Should deallocate matrix_ completely. |
void Resize(unsigned int new_rows, unsigned int new_cols) |
Resizes the matrix according to the specifications above. If new_rows or
new_cols is
invalid, throw a std::invalid_argument exception.
|
int Get(unsigned int row, unsigned int col) |
Provided: returns the value of the matrix at (row, col). |
void Set(unsigned int row, unsigned int col, int new_val) |
Provided: sets the value of the matrix at (row, col) to new_val. |
friend std::ostream& operator<<(std::ostream& os, const MatrixInt& matrix) |
Provided: prints the matrix to os. |
| Data Member | Description |
|---|---|
int** matrix_ |
Pointer to the non-empty 2D matrix. |
unsigned int rows_ |
Amount of rows (height). |
unsigned int cols_ |
Amount of cols (width) |
#include "matrix_int.hpp"
int main() {
MatrixInt matrix(3, 3);
matrix.Set(0,0,1);
matrix.Set(0,1,2);
matrix.Set(0,2,3);
matrix.Set(1,0,4);
matrix.Set(1,1,5);
matrix.Set(1,2,6);
matrix.Set(2,0,7);
matrix.Set(2,1,8);
matrix.Set(2,2,9);
std::cout << matrix << std::endl;
// matrix.Resize(2,4);
// std::cout << matrix << std::endl;
}
#ifndef MATRIX_INT_HPP
#define MATRIX_INT_HPP
#include <iostream>
#include <stdexcept>
class MatrixInt {
public:
MatrixInt(unsigned int rows, unsigned int cols);
~MatrixInt();
void Resize(unsigned int new_rows, unsigned int new_cols);
int Get(unsigned int row, unsigned int col);
void Set(unsigned int row, unsigned int col, int new_val);
friend std::ostream& operator<<(std::ostream& os, const MatrixInt& matrix);
private:
int** matrix_;
unsigned int rows_;
unsigned int cols_;
};
std::ostream& operator<<(std::ostream& os, const MatrixInt& matrix);
#endif
#include "matrix_int.hpp"
MatrixInt::MatrixInt(unsigned int rows, unsigned int cols)
: rows_{rows}, cols_{cols}, matrix_{nullptr} {
// TODO
}
MatrixInt::~MatrixInt() {
// TODO
}
void MatrixInt::Resize(unsigned int new_rows, unsigned int new_cols) {
// TODO
}
// PROVIDED - DO NOT MODIFY
int MatrixInt::Get(unsigned int row, unsigned int col) {
if (row >= rows_ || col >= cols_ || row < 0 || col < 0) {
throw std::invalid_argument("Invalid idx");
}
return matrix_[row][col];
}
void MatrixInt::Set(unsigned int row, unsigned int col, int new_val) {
if (row >= rows_ || col >= cols_ || row < 0 || col < 0) {
throw std::invalid_argument("Invalid idx");
}
matrix_[row][col] = new_val;
}
std::ostream& operator<<(std::ostream& os, const MatrixInt& matrix) {
for (unsigned int i = 0; i < matrix.rows_; ++i) {
for (unsigned int j = 0; j < matrix.cols_; ++j) {
os << matrix.matrix_[i][j] << "\t";
}
os << std::endl;
}
return os;
}
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