#include <vector.h>
#include <list.h>
#include <algo.h>
#include <iostream.h>

struct cell { // individual cell in spreadsheet
   int col_index; // column index
   float data; // contents of cell
   cell() {}
   cell(int c, float d) : col_index(c), data(d) {}
};
            
class spreadsheet {
    typedef list< cell > row_type; // rows are lists of non-empty cells

    vector< row_type > rows; // all the rows, initially empty lists
public:
    float empty_cell; // dummy float type to be returned by get_data
                      // when the cell is empty

    spreadsheet(int size) : rows(size), // number of rows in spreadsheet
                            empty_cell(0.0) {}

    float& put_data(int i, int j, float x);
       // places value x in cell at i-th row and j-th column
       // returns a reference to the data in the cell

    float& get_data(int i, int j);
       // returns a reference to the data in the cell in i-th row
       // and j-th column, or a reference to the member empty_cell

friend ostream& operator<<(ostream&, spreadsheet&);
};

class col_index_is_equal {
   // function object that compares the column index of a cell
   // to the test_index in this object which is set by the constructor
   // used in STL find generic algorithm
   int test_index; // is initialized by constructor
public:
   col_index_is_equal(int j) : test_index(j) {}
   bool operator() (const cell& c)
      {return c.col_index == test_index;}
};

float& spreadsheet::put_data(int i, int j, float x)
   {// place value x in cell at i-th row and j-th column

    if(i > rows.size()) {cerr << "row index too large in put_data";
                        return empty_cell;}

    row_type& ith_row = rows[i]; // reference to requested row

    // check if there is a cell in column j in this row
    row_type::iterator p = find_if(ith_row.begin(), ith_row.end(),
                                   col_index_is_equal(j));           
    if(p == ith_row.end())
      {// no previous cell in column j in this row, add a new cell
       ith_row.push_back( cell(j, x) );
       p = ith_row.end(); p--; // p refers to the new cell
      }
    else // previous cell in column j in this row  
      // replace the data field in that cell
      (*p).data = x;      
    return (*p).data;
   }

float& spreadsheet::get_data(int i, int j)
   {// retrieve contents of cell in i-th row and j-th column

    if(i > rows.size()) {cerr << "row index too large in get_data";
                         return empty_cell;}

    row_type& ith_row = rows[i]; // reference to requested row

    // locate cell in j-th column in this row
    row_type::iterator p = find_if(ith_row.begin(), ith_row.end(),
                                   col_index_is_equal(j));           
    if(p != ith_row.end())
      // a cell has been put there, so return its value
      return (*p).data;
    else // the cell is empty, i.e., no previous put_data for the
      // pair i and j was performed
      return empty_cell;
   }

ostream& operator<<(ostream& os, spreadsheet& sh)
   {int m, n;
    int max_row_index=-1, max_col_index=-1;

    list<cell>::iterator p;
    for(m=0; m < sh.rows.size(); m++)
       for(p = sh.rows[m].begin(); p!=sh.rows[m].end(); p++)
          {max_row_index = m;
           if((*p).col_index > max_col_index)
             max_col_index = (*p).col_index;
          }

    for(m=0; m<=max_row_index; m++)
       {for(n=0; n<=max_col_index; n++)
           {float& x = sh.get_data(m, n);
            if(&x == &sh.empty_cell)
              cout << " empty ";
            else cout << x << " ";
           }
       cout << endl; } cout << endl;}

int main(void)
{spreadsheet sh(6); // make a spreadsheet with 6 rows
 sh.put_data(1,2,3.14); // place 3.14 in row 1, col 2
 sh.put_data(1,0,-1.0); // place 3.14 in row 1, col 2
 sh.put_data(3,1,2.78); // place 2.78 in row 3, col 1
 // test if cell in row 0 and column 3 is empty
 // by comparing the address of the returned float with empty_cell
 if(&sh.get_data(0, 3) == &sh.empty_cell) cout << "empty" << endl;

 cout << sh;  // print the entire spreadsheet
}