astar.rb

@near_blocks = []
@cost = nil

def nears(i,j)
  [[i-1,j],[i+1,j],[i,j-1],[i,j+1]]
end

def near_astar map_sizes, ignores, target, current
  x = current[:x]
  y = current[:y]

  tx = target[:x]
  ty = target[:y]
  # check not goal
  return [] if nears(tx, ty).select{|n| ignores.select{|i| i[:x] == n[0] and i[:y] == n[1]}.length > 0 }.length >= 4
  
  costs = []
  positions = {}
  nears(x, y).each do |e|
    next if ignores.select{|i| i[:x] == e[0] and i[:y] == e[1]}.length > 0
    # calc cost
    if tx >= e[0]
      cost = tx - e[0]
    else
      cost = tx + e[0]
    end

    if ty >= e[1]
      cost += ty - e[1]
    else
      cost += ty + e[1]
    end

    costs << cost
    positions[cost] =  e
  end

  # retry or return if low cost?
  unless costs.empty?
    # retry or return if low cost?
    cost = nil
    loop do
      cost = costs.min
      break unless @near_blocks.include?(positions[cost])
      costs.delete cost
      return if costs.empty?
    end
    e = positions[cost]
    @cost = cost
    @near_blocks << e

    # return if bingo
    return if tx == e[0] and ty == e[1]

    # next loop
    near_astar map_sizes, ignores, target, {x: e[0], y: e[1]}
  end
end

ignores = []
near_astar({x: 10, y: 10}, ignores, {x: 5, y: 5}, {x: 8, y: 1})
p @near_blocks
@cost = nil
@near_blocks = []
ignores = [{x: 8, y: 5}, {x: 7, y:5}]
near_astar({x: 10, y: 10}, ignores, {x: 5, y: 5}, {x: 8, y: 1})
p @near_blocks

$ ruby astar.rb    
[[8, 2], [8, 3], [8, 4], [8, 5], [7, 5], [6, 5], [5, 5]]
[[8, 2], [8, 3], [8, 4], [7, 4], [6, 4], [5, 4], [5, 5]]