c++ - Specific matrix function task -
let's have function send these parameters. reference on matrix m (filled 0 , 1), coordinate x, , coordinate y. f(m,x,y). x , y coordinates of cell in matrix. function has return matrix n 3x3 format. n has filled count of how many 1's around every cell around (x,y). please @ picture in order understand better. picture not know how work way around matrix information. can please me @ least start? :d
matrix class
class matrix { private: int cols; int rows; int **cells; public: matrix(const int& x , const int& y); //constructor matrix(const matrix& m); //copy constructor int get_at(const int& x, const int& y)const; //returns value cell[x][y] void set_at(const int& x, const int& y); //sets value in cell[x][y] int get_rows()const; //returns number of rows int get_columns()const; //returns number of columns }; question: how cells in matrix m around cell[x][y]
answer: cell[x+i][y+j] i,j can -1 , 0 , 1, except case = j = 0 because thats m[x][y] obviously.
you need consider cell[x][y] can on edge of matrix , example: if x=0 , y=0, cell[x-1][anythig] or cell[anything][y-1] result in error(accessing non existent cell).
this happens if:
x+i < 0 || x+i >= m.get_rows() conclusion: x+i non existing row position
y+j < 0 || y+j >= m.get_columns() conclusion: y+i non existing column position
function count_ones
the next function counts appearance of 1 in matrix m around m.cell[x][y]
int count_ones(const matrix& m, const int& x , const int& y) { int rows = m.get_rows(); int columns = m.get_columns(); int count = 0; //iterate through cells in matrix m around m.cell[x][y] for( int = -1 ; <= 1 ; ++i) { //check row existence if( x + < 0 || x + >= rows )continue; for(int j = -1 ; j <= 1 ; ++j) { //check column existence , //avoid counting when i==0 && j==0 because thats m.cell[x][y] if( y + j = columns || ( i==0 && j==0 ) )continue; if(m.get_at(x+i,y+j) == 1 )++count;//checks m.cell[x+i][y+j]== 1 } } return count; } and function need
matrix f( const matrix& m , const int& x , const int& y ) { matrix n(3,3); for(int i=-1 ; <= 1 ; ++i )//iterate around m.cell[x][y] for(int j=-1; j <= 1 ; ++j)//-------||----------------- { //now count 1's around current cell m.cell[x+i][y+j] //and place count number inside matrix n @ right position n.set_at( i+1, j+1 , count_ones( m , x+i , y+j ) ); } return n;// make sure have copy constructor or else wont work }
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