Problem : Bishop / Rook Pawn Moves
Background
A Chess board position is accurately captured by Forsyth-Edwards notation and is abbreviated as FEN. A FEN "record" defines a particular game position, all in one text line and using only the ASCII character set. A FEN record contains six fields. A complete description of the FEN format to represent Chess positions can be found at
here.
For the purpose of this problem only consider first of the six fields of FEN. Before we describe the problem, let us look at how FEN maps to a board position. The following 5 images show board positions and its corresponding FEN representation.
Figure 1.
This board
position depicts initial position before any side has made a move.
In FEN format
this board position is represented as
rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR
w
Let's say, White
plays e4. Then the board position looks like shown below.
Figure 2.
This board
position depicts the Chess board after White has played e4.
In FEN format
this board position is represented as
rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR
b
Similarly, 3 more
half-moves are depicted in following diagrams
Figure 3.
Figure 4.
Figure 5.
The FENs
corresponding to Figure 3, 4 and 5 are represented as(in bold)
3. rnbqkbnr/pppp1ppp/8/4P3/4P3/8/PPPP1PPP/RNBQKBNR
w
4. rnbqkbnr/pppp1ppp/8/4p3/4PP2/8/PPPP2PP/RNBQKBNR
b
5. rnbqkbnr/pppp1ppp/8/8/4Pp2/8/PPPP2PP/RNBQKBNR
w
Each rank is described, starting with rank 8 and ending with rank 1; within each rank, the contents of each square are described from file "a" through file "h". Following the
Standard Algebraic Notation (SAN), each piece is identified by a single letter taken from the standard English names (pawn = "P", knight = "N", bishop = "B", rook = "R", queen = "Q" and king = "K").[1] White pieces are designated using upper-case letters ("PNBRQK") while black pieces use lowercase ("pnbrqk"). Empty squares are noted using digits 1 through 8 (the number of empty squares), and "/" separates ranks.
The second field denotes whose move it is now. "w" depicts that it is White's turn to play and "b" indicates that it is Black's turn to play
CodeVita Problem Statement
Given a board position in FEN format, your task is to find out all the move(s) that Bishop(s) of the playing side can make.
Input Format:
1.
First line contains single FEN record, which
corresponds to a particular board position and also indicates whose turn it is.
Output Format:
1.
The output must be printed as follows
2.
All legal moves that Bishop can make must be in
the format "[<Move Format>]"
3.
Where <Move Format> is
move represented in format "[fromSquare][toSquare]"
4.
See Example section for better understanding of
output format.
5.
Follow Output printing specification to print
the output in required format.
Constraints:
1.
Since we focus on only first two parts of the
FEN, we are essentially ignoring possibility of Castling. Hence our test cases
don't contain FENs which give rise to such positions.
Sample
Input and Output
Board Depiction 1:
Output 1: []
Sample 2 input: 3k4/8/8/2P1P3/3B4/2R1R3/8/4K3 w
Board Depiction 2:
Output 2: [d4a7, d4b6, d4c5]
Sample 3 input: 3k4/8/8/2P1P3/3B4/2R1R3/8/4K3 w
Board Depiction 3:
Output 3: [d4h8, d4a7, d4g7, d4b6, d4f6, d4c5, d4e5, d4c3, d4e3, d4b2, d4f2, d4a1, d4g1, b1h7, b1g6, b1f5, b1e4, b1d3, b1a2, b1c2]
1.
Should start with "[" and end with
"]"
2.
If more than one move is possible, moves should
be separated by a comma followed by whitespace
3.
Moves of a single bishop should be printed in
Move Format. Scan the board from 8th rank to 1st rank from a-file to h-file.
Whichever square gets hit first, that move should be printed first.
4.
If more than one bishop exists for side to move,
then start scanning for bishop from 8th rank to 1st rank, left to right i.e.
from a-file to h-file. Whichever bishop appears first, print all moves for that
bishop first.
5.
Verify your understanding of how printing should
happen against examples shown above
TCS CodeVita 2016 Round1 Question: Bishop / Rook Pawn Moves
C-Language Program (MockVita2/pawnmoves.c)
#include <stdio.h>
#include <stdbool.h>
#define BLACK 0
#define WHITE 1
char board[8][8];
int current;
void readBoard();
void findPawnMoves();
void printMove(char, int, int, int, int);
int main()
{
readBoard();
findPawnMoves();
return 0;
}
void readBoard()
{
char c = '\0';
int row = 0;
int col = 0;
int i;
while (c != ' ')
{
scanf("%c", &c);
if (c == '/')
{
row++;
col = 0;
continue;
}
if (c >= '0' && c <= '9')
{
for (i = 0; i < c - '0'; i++)
board[row][col++] = ' ';
continue;
}
board[row][col++] = c;
}
scanf("%c", &c);
current = c == 'w' ? WHITE : BLACK;
}
void findPawnMoves()
{
int i, j;
int factor = current == BLACK ? 1 : -1;
char pawn = current == BLACK ? 'p' : 'P';
char other;
printf("[");
for (j = 0; j < 8; j++)
{
if (current == BLACK && j == 7)
continue;
if (current == WHITE && j == 0)
continue;
for (i = 7; i > -1; i--)
if (board[i][j] == pawn)
{
if (j != 0)
{
other = board[i + factor][j - 1];
if (other != ' ')
printMove(other, i, j, i - 1, j + factor);
}
other = board[i + factor][j];
if (other == ' ')
printMove(other, i, j, i + factor, j);
if (current == BLACK && i == 1)
{
other = board[i + factor * 2][j];
if (other == ' ')
printMove(other, i, j, i + factor * 2, j);
}
if (current == WHITE && i == 6)
{
other = board[i + factor * 2][j];
if (other == ' ')
printMove(other, i, j, i + factor * 2, j);
}
if (j != 7)
{
other = board[i + factor][j + 1];
if (other != ' ')
printMove(other, i, j, i + 1, j + factor);
}
}
}
printf("]");
}
void printMove(char other, int i1, int j1, int i2, int j2)
{
static bool firstMove = true;
if ((current == BLACK && other >= 'A' && other <= 'Z') ||
(current == WHITE && other >= 'a' && other <= 'z') ||
other == ' ')
{
if (!firstMove)
printf(", ");
firstMove = false;
printf("%c%d%c%d", 'a' + j1, 8 - i1, 'a' + j2, 8 - i2);
}
}
Sources:
https://www.programminggeek.in/
https://github.com/