c++ - Vectors 2D first usage -

c++ - Vectors 2D first usage -

it first time utilize 2d vectors in c++ , seems i'm trying access forbidden location although indexes of loops less size

int generate_(vector<int> row,vector<int> column) { int i=1,j=1,k=0,l=0; vector<vector<int > >matrix;//2d vector for(k=0,l=0;l<column.size();l++) { matrix[k][l]=row[l]; cout << matrix[k][l]<<endl; } for(k=0,l=0;l<row.size();l++) matrix[l][k]=column[l]; for(i=1;i<row.size();i++) { for(j=1;j<column.size();j++) { matrix[i][j]=matrix[i][j-1]+matrix[i-1][j]+matrix[i-1][j-1]; } } homecoming matrix[i-1][j-1]; }

matrix not initialized, has no elements matrix[k][l] raise exception

c++ vector