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113 lines
3.1 KiB
Python
113 lines
3.1 KiB
Python
''' mbinary
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#########################################################################
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# File : 8Astar.py
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# Author: mbinary
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# Mail: zhuheqin1@gmail.com
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# Blog: https://mbinary.coding.me
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# Github: https://github.com/mbinary
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# Created Time: 2018-05-19 23:06
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# Description:
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#########################################################################
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'''
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isVisited = [0]*362880 # 0 for not visited,1 for occured,2 for visited
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fac = [1,1,2,6,24,120,720,5040,40320]
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lf = len(fac)
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h = [[0,1,2,1,2,3,2,3,4],
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[1,0,1,2,1,2,3,2,3],
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[2,1,0,3,2,1,4,3,2],
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[1,2,3,0,1,2,1,2,3],
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[2,1,2,1,0,1,2,1,2],
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[3,2,1,2,1,0,3,2,1],
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[2,3,4,1,2,3,0,1,2],
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[3,2,3,2,1,2,1,0,1],
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[4,3,2,3,2,1,2,1,0]]
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def cantor(s):
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sum = 0
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ls = len(s)
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for i in range(ls):
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count = 0
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for j in range(i+1,ls):
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if s[i] > s[j]: count +=1
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sum += count*fac[lf-i-1]
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return sum
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que = []
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dir = {-3:'u',1:'r',3:'d',-1:'l'}
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class state:
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flag = True
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def __init__(self,s,x,f,step=0,last=0):
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self.x = x
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self.s = list(s)
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self.step = step
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self.path = []
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self.last = last
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self.f = f
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def can(self):
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cans = [-1,1,3,-3]
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if self.last in cans :
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cans.remove(-self.last)
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if self.x<3:
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cans.remove(-3)
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if self.x>5:
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cans.remove(3)
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if self.x%3 is 0:
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cans.remove(-1)
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if self.x%3 is 2:
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cans.remove(1)
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return cans
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def move(self):
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cans = self.can()
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for i in cans:
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s = list(self.s)
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tmp = self.x + i
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s[self.x] = s[tmp]
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s[tmp] = '9'
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ct = cantor(s)
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if isVisited[ct] != 2 :
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val = int(s[self.x])
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f = h[8][tmp] +h[val-1][self.x]-h[8][self.x]-h[val-1][tmp]+self.step+1
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new = state(s,tmp,f,self.step +1,i)
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new.path = self.path + [dir[i]]
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if isVisited[ct] == 1:
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for i,node in enumerate(que):
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if mew.s == node.s:
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del que[i]
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break
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else:isVisited[ct] = 1
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if que == []:
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que.append(new)
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continue
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for i,node in enumerate(que):
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if new.f<=node.f:
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que.insert(i,new)
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def solvable(s):
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reverse = 0
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for i in range(8):
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if s[i] is '9':continue
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for j in range(i+1,9):
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if s[i]>s[j]:reverse +=1
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if reverse % 2 is 0:return True
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else:return False
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def getPath(s,index):
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f = 0
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for i,j in enumerate(s):
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f+=h[int(j)-1][i]
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que.append(state(s,index,f,0,0))
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while que != []:
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cur = que.pop(0)
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ct = cantor(cur.s)
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isVisited[ct] = 2
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if ct is 0:
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return cur.path
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cur.move()
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if __name__ == '__main__':
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s=input()
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index = s.find('x')
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s =list(s)
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s[index] = '9'
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if solvable(s):print(''.join(getPath(s,index)))
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else:print('unsolvable')
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