void b19(int* position)
{
const char knight = 'K'; // symbol of Knight
const char capture = 'X'; // symbol of captured field
const char empty = '.'; // symbol of empty field
int moves[2] = {1, 2}; // length of knight's moves: one or two cells
int directions[2] = {-1, 1}; // direction of knight's moves: up/down in either dimension
char board[size][size]; // our chessboard
// initialize board; mark all squares as empty
for(int rank = size-1; rank >= 0; rank--)
for(int file = 0; file < size ; file++)
board[rank][file] = empty;
int file = position[0]; // file is a chessboard term for a column
int rank = position[1]; // rank is a chessboard term for a row
board[rank][file] = knight; // mark knight's position on board
//
// the BIG loop for calculating knight's captured squares
//
// for each direction - up or down - for rank ..
for (int rank_direction = 0; rank_direction <= 1; rank_direction++)
{
// .., and for each possible move - 1 or 2 cells, on rank..
for (int rank_move = 0; rank_move <= 1; rank_move++)
{
// .., and for each possible direction for file:
for (int file_direction = 0; file_direction <= 1; file_direction++)
{
// calculate move per file
// (trick is, if you move knight ONE cell right, you can move just TWO cells up or down)
int file_move = rank_move? moves[0] : moves[1];
int file_captured = file + directions[file_direction] * file_move;
int rank_captured = rank + directions[rank_direction] * moves[rank_move];
if
(
// if file and rank are on board (1..8)
is_on_board(file_captured) &&
is_on_board(rank_captured)
)
{
// then mark this square as captured
board[rank_captured][file_captured] = capture;
}
}
}
}
print_chessboard(board, position);
}
// converts input of 'a' or 'A' to 0 (first file)
int to_file(int file)
{
const int uppercase = 'A'; // ASCII code for char 'A'
const int lowercase = 'a'; // ASCII code for char 'a'
if (is_on_board(file, uppercase))
{
file -= uppercase;
}
else if (is_on_board(file, lowercase))
{
file -= lowercase;
}
return file;
}
int* request_position()
{
int* position = new int[2];
position[0] = -1; // filling with incorrect data to start loop
position[1] = -1;
string answer;
while (!is_on_board(position))
{
print("Enter knight's position, from a1 to h8: ");
cin >> answer;
position[0] = to_file(answer[0]);
position[1] = to_rank(answer[1]);
if (!is_on_board(position))
{
print("You have entered incorrect data.");
}
}
return position;
}
bool is_on_board(int file, int char_code)
{
return is_on_board(file - char_code);
}
// checks if position is on board (a1 till h8 - [0][0] till [7][7])
bool is_on_board(int *position)
{
return is_on_board(position[0]) &&
is_on_board(position[1]);
}
// -------------------------------------------------------------------
// Determine whether the given square is under attack by a given side
// -------------------------------------------------------------------
bool ChessBoard::is_attacked(bool by_white, int to) const {
int from, i;
const int ahead=by_white?-1:1;
// Check for pawn attacks
from=to+ahead*Rank-File;
if (is_on_board(from) && square[from]==make_colour(Pawn, by_white) &&
abs(which_file(from)-which_file(to))==1)
return true;
from=to+ahead*Rank+File;
if (is_on_board(from) && square[from]==make_colour(Pawn, by_white) &&
abs(which_file(from)-which_file(to))==1)
return true;
// Check for bishop/queen attacks
static const int b_increment[]={-Rank-File, Rank-File, -Rank+File,
Rank+File};
for(i=0;i<4;i++) {
for (from=to+b_increment[i]; is_on_board(from) &&
abs(which_file(from)-which_file(from-b_increment[i]))==1;
from+=b_increment[i]) {
if (square[from]==make_colour(Bishop, by_white) ||
square[from]==make_colour(Queen, by_white))
return true;
if (square[from]!=Empty)
break;
}
}
// Check for rook/queen attacks
static const int r_increment[]={-Rank, Rank, -File, File};
for(i=0;i<4;i++) {
for (from=to+r_increment[i]; is_on_board(from) &&
abs(which_file(from)-which_file(from-r_increment[i]))<=1;
from+=r_increment[i]) {
if (square[from]==make_colour(Rook, by_white) ||
square[from]==make_colour(Queen, by_white))
return true;
if (square[from]!=Empty)
break;
}
}
// Check for knight attacks
static const int n_source[] = {-2*Rank-File, -2*Rank+File, -2*File-Rank,
-2*File+Rank, 2*Rank-File, 2*Rank+File, 2*File-Rank, 2*File+Rank};
for (i=0;i<8;i++) {
from=to+n_source[i];
if (is_on_board(from) && square[from]==make_colour(Knight, by_white) &&
abs(which_file(from)-which_file(to))<3)
return true;
}
// Check for king attacks
static const int k_source[] = {-Rank-File, -Rank, -Rank+File, -File,
File, Rank-File, Rank, Rank+File};
for (i=0;i<8;i++) {
from=to+k_source[i];
if (is_on_board(from) && square[from]==make_colour(King, by_white) &&
abs(which_file(from)-which_file(to))<=1)
return true;
}
// Check for en passant attacks
if (to-ahead*Rank==en_passant &&
(square[to-File]==make_colour(Pawn, by_white) ||
square[to+File]==make_colour(Pawn, by_white)))
return true;
return false;
}