Question

我有2个水壶的问题。初始状态为[0,0]，每个壶的容量为[4,9]，目标状态为[0,6] 合法动作：将壶1或壶2填到最后，将空壶1或壶2和可怜的壶放入另一壶中。

import search #get the interface
import sys
sys.setrecursionlimit(5000)
class two_jugs(search.Nodes):

    #return the starting state vessel 1: 0, vessel 2: 0
    def start(self):
            return [0,0]

    #returns true if node is equal to goal node
    def goal(self,node):
            return node ==(0,6)
    #yields the successors of the configuration indicated by node
    def succ(self,node):             
            # set capacities for vessel 1: 4, vessel 2 : 9
            c = [4,9];
            #stop at second last
            for i in range(len(node)-1):
                    #create a safety copy
                    new_node = node[:]

                    #fill vessel 1
                    if new_node[i]<=0:
                            new_node[i]=c[i]
                            print new_node

                    #fill vessel 2
                    if new_node[i+1]<=0:
                            new_node[i+1]=c[i+1]
                            print new_node

                    #dump vessel i+1
                    if (new_node[i+1]>0):
                            new_node[i+1]=0
                            print new_node

                    #poor vessel i to vessel i+1                
                    if (new_node[i+1]<c[i+1] and new_node[i]>0):
                            #calculate the difference
                            d = min(new_node[i],c[i+1]-new_node[i+1])
                            new_node[i]= new_node[i]-d
                            new_node[i+1]= new_node[i+1]+d
                            print new_node

                    #dump vessel i
                    if (new_node[i]>0):
                            new_node[i]=0
                            print new_node


               #poor vessel i+1 to vessel 1
                    if (new_node[i]<c[i] and new_node[i+1]>0):
                            #calculate the difference
                            d = min(new_node[i+1],c[i]-new_node[i])
                            #set new node
                            new_node[i+1]= new_node[i+1]-d
                            new_node[i]= new_node[i]+d
                            yield new_node
                            print new_node

问题是，由于我已经宣布了所有法律行动，为什么我的计划只返回一项法律行动的结果？例如，当我运行程序时从起始状态[0,0]返回[4,0]，[0,4]，[0,9]和其他可能的结果，直到递归停止但不是我的目标状态。我错过了什么？

breadth_first_search类：

def breadth_first_search(problem, candidates):
    if not candidates: return
    # make sure there is something in the candidate list
    # I am modifying ’candidates’ list here.
    # Why don’t I need to copy?
    c = candidates.pop(0) # pop from front
    node = c[-1] # must exist
    if problem.goal(node): return c
    # base case
    succ = [s for s in problem.succ(node)]
    for s in problem.succ(node):
        candidates.append(c + [s])
        # 1-step extension
    return breadth_first_search(problem, candidates)

搜索课程：

class Nodes:
    def succ(self,n):
        raise Exception, "Successor undefined"
    def start (self):
        raise Exception, "Start undefined"
    def goal (self,n):
        raise Exception, "Goal undefined"

运行程序的类：

import decant
from breadth_first_search import *

dec = decant.Decant()
print breadth_first_search(dec,[[dec.start()]])

Answer 1

你的第一个错误是标记班级2jugs。 python中的变量名（包括类和函数的名称）以及许多其他编程语言都不能以数字开头。因此，请将2jugs重命名为two_jugs。

precise rule for identifiers in python是标识符必须以大写（A-Z），小写（a-z）或下划线（_）开头。标识符的以下字符也可以包含数字（0-9）。（该规则在Backus-Naur form）中指定。

Python递归我错过了什么

1 个答案: