#!/usr/bin/python # vim:set fileencoding=utf-8 # 在春节放假前两天我偶然看到了A*算法，感觉挺有意思。正好放假前 # 也没有什么事情，就花了一个下午写出算法的骨架，节后又花了半天 # 时间完善屏幕输出的细节并且调试完成。 # 该实现只是一时兴起的随手而作，没有考虑性能和扩展性等问题。正 # 在学习A*的朋友可以拿去随便折腾。 # email: wang.zhigang@hotmail.com import sys _2dmap = [] start = None end = None open_list = {} close_list = {} map_border = () class Node: def __init__(this, father, x, y): if x < 0 or x >= map_border[0] or y < 0 or y >= map_border[1]: raise Exception("node position can't beyond the border!") this.father = father this.x = x this.y = y if father != None: G2father = calc_G(father, this) if not G2father: raise Exception("father is not valid!") this.G = G2father + father.G this.H = calc_H(this, end) this.F = this.G + this.H else: this.G = 0 this.H = 0 this.F = 0 def reset_father(this, father, new_G): if father != None: this.G = new_G this.F = this.G + this.H this.father = father def calc_G(node1, node2): x1 = abs(node1.x-node2.x) y1 = abs(node1.y-node2.y) if (x1== 1 and y1 == 0): return 10 # same row if (x1== 0 and y1 == 1): return 10 # same col if (x1== 1 and y1 == 1): return 14 # cross else: return 0 def calc_H(cur, end): return abs(end.x-cur.x) + abs(end.y-cur.y) # NOTE 这个地方可能成为性能瓶颈 def min_F_node(): if len(open_list) == 0: raise Exception("not exist path!") _min = 9999999999999999 _k = (start.x, start.y) for k,v in open_list.items(): if _min > v.F: _min = v.F _k = k return open_list[_k] # 把相邻节点加入open list, 如果发现终点说明找到了路径 def addAdjacentIntoOpen(node): # 将该节点从开放列表移到关闭列表当中。 open_list.pop((node.x, node.y)) close_list[(node.x, node.y)] = node _adjacent = [] # 相邻节点要注意边界的情况 try: _adjacent.append(Node(node , node.x - 1 , node.y - 1)) except Exception,e: pass try: _adjacent.append(Node(node , node.x , node.y - 1)) except Exception,e: pass try: _adjacent.append(Node(node , node.x + 1 , node.y - 1)) except Exception,e: pass try: _adjacent.append(Node(node , node.x + 1 , node.y)) except Exception,e: pass try: _adjacent.append(Node(node , node.x + 1 , node.y + 1)) except Exception,e: pass try: _adjacent.append(Node(node , node.x , node.y + 1)) except Exception,e: pass try: _adjacent.append(Node(node , node.x - 1 , node.y + 1)) except Exception,e: pass try: _adjacent.append(Node(node , node.x - 1 , node.y)) except Exception,e: pass for a in _adjacent: if (a.x,a.y) == (end.x, end.y): new_G = calc_G(a, node) + node.G end.reset_father(node, new_G) print "find path finish!" return True if (a.x,a.y) in close_list: continue if (a.x,a.y) not in open_list: open_list[(a.x,a.y)] = a else: exist_node = open_list[(a.x,a.y)] new_G = calc_G(a, node) + node.G if new_G < exist_node.G: exist_node.reset_father(node, new_G) return False def find_the_path(start, end): open_list[(start.x, start.y)] = start the_node = start try: while not addAdjacentIntoOpen(the_node): the_node = min_F_node() except Exception,e: # path not exist print e return False return True #======================================================================= def print_map(): print ' Y', for i in xrange(len(_2dmap)): print i, print print ' X' row = 0 for l in _2dmap: print '%3d'%row,' ', row = row+1 for i in l: print i, print def mark_path(node): if node.father == None: return _2dmap[node.x][node.y] = '#' mark_path(node.father) def preset_map(): global start,end,map_border _2dmap.append('S X . . . . . . . . . . . . . X . . . .'.split()) _2dmap.append('. X . . . . . . . . . . . . . X . . . .'.split()) _2dmap.append('. X . . . . . . . . . . . . . X . . . .'.split()) _2dmap.append('. . . . . . . . . . . . . . . X . . . .'.split()) _2dmap.append('. . . . . . . . . . . . . . . X . . . .'.split()) _2dmap.append('. . . . . . . . . . . . . . . . . . . .'.split()) _2dmap.append('. . . . . . . . . . . . . . . X X X X .'.split()) _2dmap.append('. . . . . . . . . . . . . . . X . . . .'.split()) _2dmap.append('. . . . . . . . . . . . . . . X . X X X'.split()) _2dmap.append('. . . . . . . . . . . . . . . X . X . .'.split()) _2dmap.append('. . . . . . . . . . . . . . . X . . . .'.split()) _2dmap.append('. . . . . . . . . . . . . . . X . X . .'.split()) _2dmap.append('. . . . . . . . . . . . . . . X . X . .'.split()) _2dmap.append('. . . . . . . . . . . . . . . X . X . .'.split()) _2dmap.append('. . . . . . . . . . . . . . . X . X . .'.split()) _2dmap.append('. . . . . . . . . . . . . . . X . X . E'.split()) map_border = (len(_2dmap),len(_2dmap[0])) row_index = 0 for row in _2dmap: col_index = 0 for n in row: if n == 'X': block_node = Node(None, row_index, col_index) close_list[(block_node.x, block_node.y)] = block_node elif n == 'S': start = Node(None, row_index, col_index) elif n == 'E': end = Node(None, row_index, col_index) col_index = col_index + 1 row_index = row_index + 1 if __name__=='__main__': if len(sys.argv) < 3: preset_map() else: x = int(sys.argv[1]) y = int(sys.argv[2]) map_border = (x,y) _start = raw_input('pls input start point:') _end = raw_input('pls input end point:') _start = _start.split(',') _end = _end.split(',') _start = (int(_start[0]), int(_start[1])) _end = (int(_end[0]), int(_end[1])) start = Node(None, _start[0], _start[1]) end = Node(None, _end[0], _end[1]) # gen map _2dmap = [['.' for i in xrange(y)] for i in xrange(x) ] # put start and end _2dmap[_start[0]][_start[1]] = 'S' _2dmap[_end[0]][_end[1]] = 'E' # input blocks while True: _block = raw_input('input block:') if not _block: break _block = _block.split(',') _block = (int(_block[0]), int(_block[1])) _2dmap[_block[0]][_block[1]] = 'X' block_node = Node(None, _block[0], _block[1]) close_list[(block_node.x, block_node.y)] = block_node print "orignal map:" print_map() if find_the_path(start, end): mark_path(end.father) print "found road as follow:" print_map()
