我目前正在执行Knight's Travails项目。在这个项目中,您需要找到国际象棋骑士从A到B的最短路程。
我不知道为什么广度优先搜索功能导致我的程序崩溃。我无法通过调试器捕获它,因为VScode在读取knight_moves中的变量“ root”时冻结了。
您能帮我找到使用方法吗?
我创建了董事会。它根据单元的位置链接到电路板上的每个单元。我已经使用add_edges函数在单元格之间创建了链接。链接是可能的移动方式。
到目前为止,我已经在下面的代码中
class Node
attr_reader :pos
attr_accessor :children, :search_info
def initialize (row, column)
@pos = [row, column]
@children = nil
@search_info = Hash.new
end
end
class Board
attr_reader :show
def initialize
create_board
end
def create_board
board = []
8.times do |x|
board<<[x]
end
board.each_with_index do |item, index|
8.times do |x|
board[index] << x unless x == index
end
end
board.each do |x|
x.sort!
end
@board = board
end
def show
@board
end
def fill_with_nodes
@board.each_with_index do |item, index|
item.map! {|column| Node.new(index,column)}
end
end
def add_edges
@board.each_with_index do |row, index|
row.each do |node|
node.children = []
node.children = node.children << @board[node.pos[0]-2][node.pos[1]-1] if (0..7).include?(node.pos[0]-2) && (0..7).include?(node.pos[1]-1)
node.children = node.children << @board[node.pos[0]-2][node.pos[1]+1] if (0..7).include?(node.pos[0]-2) && (0..7).include?(node.pos[1]+1)
node.children = node.children << @board[node.pos[0]+2][node.pos[1]-1] if (0..7).include?(node.pos[0]+2) && (0..7).include?(node.pos[1]-1)
node.children = node.children << @board[node.pos[0]+2][node.pos[1]+1] if (0..7).include?(node.pos[0]+2) && (0..7).include?(node.pos[1]+1)
node.children = node.children << @board[node.pos[0]-1][node.pos[1]-2] if (0..7).include?(node.pos[0]-1) && (0..7).include?(node.pos[1]-2)
node.children = node.children << @board[node.pos[0]+1][node.pos[1]-2] if (0..7).include?(node.pos[0]+1) && (0..7).include?(node.pos[1]-2)
node.children = node.children << @board[node.pos[0]-1][node.pos[1]+2] if (0..7).include?(node.pos[0]-1) && (0..7).include?(node.pos[1]+2)
node.children = node.children << @board[node.pos[0]+1][node.pos[1]+2] if (0..7).include?(node.pos[0]+1) && (0..7).include?(node.pos[1]+2)
end
end
end
def cell (row, column)
@board[row][column]
end
def knight_moves (start, finish)
raise StandardError.new("Invalid start") unless (0..7).include?(start[0]) || (0..7).include?(start[1])
raise StandardError.new("Invalid finish") unless (0..7).include?(finish[0]) || (0..7).include?(finish[1])
queue = []
root = @board[finish[0]][finish[1]]
root.search_info[:distanse] = 0
queue << root
until queue.empty?
node = queue.shift
break if node.pos == [start[0],start[1]]
node.children.each do |child|
unless child.search_info[:distanse]
child.search_info[:distanse] = node.search_info[:distanse] + 1
child.search_info[:predecessor] = node
queue << child
end
end
end
end
end
#This part is for testing
puts a = Board.new
puts a.show.to_s
a.fill_with_nodes
puts a.show.to_s
a.add_edges
a.knight_moves([0,0], [0,1])
def show_cell(board,row, column)
puts ""
puts board.cell(row,column).pos.to_s, board.cell(row,column).children.map {|child| child.pos}.to_s ,board.cell(row,column).search_info.to_s
end
show_cell(a,2,2)
编辑:我发现“ child.search_info [:predecessor] = node”行使程序崩溃。而且,如果我使用@variable来存储“前任”而不是哈希,则程序将运行。我不知道为什么。什么原因?
对我来说,代码的主要问题是它不必要的(偶然的)复杂性。
是的,您要解决的任务可以简化为图遍历的问题,但是这并不意味着您必须明确表示图]。对于此特定任务-从任意单元格开始的所有可能移动均已定义好,并且电路板本身受到限制-您可以轻松地动态计算图形边缘(并且无需使用所有其他会使机器难以推理的额外机制)关于-甚至是您)。董事会的明确表示也显得多余(再次针对此特定任务)。
考虑到所有这些,解决方案可能很简单:
class Knight
def initialize
@knight_moves = [[-2, -1], [-2, 1], [-1, -2], [-1, 2], [1, -2], [1, 2], [2, -1], [2, 1]]
end
def move(start, stop)
visited = {}
queue = [[stop, nil]]
while queue.any?
current_cell, next_cell = queue.shift
next if visited.has_key?(current_cell)
visited[current_cell] = next_cell
return build_path(start, stop, visited) if current_cell == start
possible_moves(current_cell).each do |next_move|
queue << [next_move, current_cell] unless visited.has_key?(next_move)
end
end
end
private
def possible_moves(cell)
@knight_moves.
map { |x, y| [cell.first + x, cell.last + y] }.
select(&method(:valid_move?))
end
def build_path(start, stop, visited)
path = [start]
while next_cell = visited[path.last]
path << next_cell
end
path.last == stop ? path : nil
end
def valid_move?(cell)
cell.all? { |n| n >= 0 && n <= 7 }
end
end
knight = Knight.new
knight.move [0,0], [0,1] #=> [[0, 0], [2, 1], [1, 3], [0, 1]]