import string

class Node:

   def __init__ (self,state):
      self.state = state

def makeNodes(n,states):
   return [Node(s) for s in states]

def successors(node):
   """ return a list of all legal successor states of 
   node.state"""
   print("Enter successors of ", node.state, "(in a list) ",)
   return input(" --> ")

def goalp(node):
   """ return 1 if node.state is a goal; 0 otherwise."""

   print("Is ", node.state, "a goal (0 for no, 1 for yes)",)
   x = input("? ")
   return x

def treesearch(qfun, fringe):
   while fringe:
      cur = fringe[0]
      fringe = fringe[1:]
      if goalp(cur)=='1':
         return cur
      fringe = qfun(makeNodes(cur,successors(cur)), fringe)
   return []

def graphsearch(qfun, fringe):
   expanded = {}
   while fringe:
      cur = fringe[0]
      fringe = fringe[1:]
      if goalp(cur)=='1':
         return cur
      if not (cur.state in expanded and\
          expanded[cur.state].gval <= cur.gval):
         expanded[cur.state] = cur
         fringe = qfun(makeNodes(cur,successors(cur)), fringe)
   return []

def myappend(list1, list2):
   return list1 + list2

def prepend(list1, list2):
   return list2 + list1

def depthfirstsearch(start):
    return treesearch (myappend, [Node(start)])

def depthfirstsearch1(start):
    return graphsearch (myappend, [Node(start)])

def breadthfirstsearch(start):
    return treesearch (prepend, [Node(start)])

def bestfirstsearch(start):
    """ Called greedy best-first search in Russell & Norvig 2nd edition"""
    return treesearch(mysort,[Node(start)])

def comparestates(state1,state2):
   return cmp(h(state1),h(state2))

def mysort (list1, list2):
   total = list1 + list2
   total.sort(comparestates)
   return total

print("Let's start with breadth first search:")
result = breadthfirstsearch("a")
if result == []:
   print(result)
else:
   print(result.state)

print("Now depth first search, checking for repeated states:")
result = depthfirstsearch1("a")
if result == []:
   print(result)
else:
   print(result.state)


"""
CHANGELOG
(08/30/2013: ported by charmgil)
- 'print' has been replaced with 'print()'
- Condition for the if statements on line#39,49 is specified more explicitly,
 for goalp(cur) returns a char type value (character '0' is also considered as true)
- 'expanded.has_key(cur.state)' on line#51 has been removed, since the function is deprecated
    - Note that the initialization on line#45 ('expanded = {}') is still valid
"""