Knight Tour

Problem Description

* Input Predicates: size/1 givenmove/4

* Output Predicates: move/4

Find a tour for the knight piece that starts at any square, travels all squares, and comes back to the origin, following the rules of chess.

Input format

The input file contains one atom size(N), which states that the chess board size is N*N and a number of atoms givenmove(X1,Y1,X2,Y2). The rows of the board are numbered 1, 2, and so on up to N from top to bottom, and the columns are numbered 1, 2, and so on up to N from left to right. In this way, each square can be represented by a unique pair of coordinates.

Output format

The output is a tour defined as a predicate

move(X1,Y1,X2,Y2). move(X2,Y2,X3,Y3). ... move(Xn,Yn,X1,Y1).

where each atom represents a valid move of the knight, all the squares are connected, and the last move brings the knight back to the origin. Moreover, the path contains all moves specifices by the givenmove predicate.

Example

size(8). givenmove(7,5,8,7). givenmove(1,7,3,6).

move(1,1,2,3). move(2,3,4,2). move(4,2,2,1). move(2,1,1,3). move(1,3,2,5). move(2,5,3,7). move(3,7,1,8). move(1,8,2,6). move(2,6,1,4). move(1,4,2,2). move(2,2,3,4). move(3,4,1,5). move(1,5,2,7). move(2,7,4,6). move(4,6,5,8). move(5,8,6,6). move(6,6,5,4). move(5,4,7,5). move(7,5,8,7). move(8,7,6,8). move(6,8,4,7). move(4,7,2,8). move(2,8,1,6). move(1,6,3,5). move(3,5,4,3). move(4,3,5,5). move(5,5,7,4). move(7,4,8,2). move(8,2,6,1). move(6,1,7,3). move(7,3,8,1). move(8,1,6,2). move(6,2,4,1). move(4,1,3,3). move(3,3,4,5). move(4,5,5,3). move(5,3,7,2). move(7,2,5,1). move(5,1,6,3). move(6,3,7,1). move(7,1,8,3). move(8,3,6,4). move(6,4,8,5). move(8,5,7,7). move(7,7,6,5). move(6,5,8,4). move(8,4,7,6). move(7,6,8,8). move(8,8,6,7). move(6,7,8,6). move(8,6,7,8). move(7,8,5,7). move(5,7,3,8). move(3,8,1,7). move(1,7,3,6). move(3,6,4,8). move(4,8,5,6). move(5,6,4,4). move(4,4,5,2). move(5,2,3,1). move(3,1,1,2). move(1,2,2,4). move(2,4,3,2). move(3,2,1,1).

Notes

Appeared at 2nd ASP competition - 2009 Original Author: Neng-Fa Zhou, Affiliation: CUNY Brooklyn College