Python算法之24点游戏

　　问题:输入任意的四个数字，这四个数字的取值范围：1~13，这个四个数经过任意的加、减、乘、除四则运算的结果是24，并输出这四个数所有的运算结果为24的可能计算方式组合。
　　例如，输入1,2,6,4
　　输出:4*6/(2-1)=26
　　(2-1)*4*6=24
　　(2+6)*(4-1)=24
　　((2-1)*6)*4=24
　　代码:from itertools import combinations import re from numpy import random  class Solver:     # 目标值     target = 24     # 四则运算符     ops = [＂+＂, ＂-＂, ＂*＂, ＂/＂, ＂--＂, ＂//＂]      def __init__(self, precise_mode=False):         self.preprecise_mode = precise_mode      def solution(self, nums):         result = []         groups = self.dimensionality_reduction(self.format(nums))         for group in groups:             for op in self.ops:                 exp = self.assemble(group[0], group[1], op)[＂exp＂]                 if self.check(exp, self.target) and exp not in result:                     result.append(exp)         return [exp + ＂=＂ + str(self.target) for exp in result]      # 降维     def dimensionality_reduction(self, nums):         result = []         if len(nums) > 2:             for group in self.group(nums, 2):                 for op in self.ops:                     new_group = [self.assemble(group[0][0], group[0][1], op)] + group[1]                     result += self.dimensionality_reduction(new_group)         else:             result = [nums]         return result      # 将两个表达式组合成一个     def assemble(self, exp1, exp2, op):         if op == ＂--＂ or op == ＂//＂:             return self.assemble(exp2, exp1, op[0])         if op in r＂*/＂:             exp1 = self.add_parenthesis(exp1)             exp2 = self.add_parenthesis(exp2)         if self.preprecise_mode:             if op == ＂-＂:                 exp2 = self.add_parenthesis(exp2)             elif op == ＂/＂:                 exp2 = self.add_parenthesis(exp2, True)         exp = self.convert(exp1[＂exp＂] + op + exp2[＂exp＂], op)         return {＂op＂: op, ＂exp＂: exp}      # 根据需要为表达式添加相应的括号     @staticmethod     def add_parenthesis(exp, is_necessary=False):         if (is_necessary and not exp[＂exp＂].isdigit()) or exp[＂op＂] in r＂+-＂:             result = {                 ＂exp＂: ＂(＂ + exp[＂exp＂] + ＂)＂,                 ＂op＂: exp[＂op＂]             }         else:             result = exp         return result      @staticmethod     def check(exp, target, precision=0.0001):         try:             return abs(eval(exp) - target) < precision         except ZeroDivisionError:             return False     #将表达式各项重新排序为等价的表达式     @staticmethod     def convert(exp, op):         if op in r＂+-＂:             pattern = r＂([+-](((.+)|d+)[*/]((.+)|d+)|d+))＂             exp = ＂+＂ + exp         else:             pattern = r＂([*/]((.+?)|d+))＂             exp=＂*＂+exp         result = ＂＂.join(sorted(i[0] for i in re.findall(pattern, exp)))         if len(result) != len(exp):             result = exp         return result[1:]      # 将输入的数字格式化为字典     @staticmethod     def format(nums):         return [{＂op＂: ＂ ＂, ＂exp＂: str(num)} for num in nums]      @staticmethod     def group(exp_list, counter):         # 生成以下标号为元素的列表         index_list = [i for i in range(len(exp_list))]         # 以下标号列表取出不重复的组合         combination = list(combinations(index_list, counter))          for group1 in combination:             group2 = list(set(index_list) - set(group1))             yield [                 [exp_list[g1] for g1 in group1],                 [exp_list[g2] for g2 in group2]             ]   if __name__ == ＂__main__＂:     auto_input = False     if auto_input:         customer_input = random.randint(1, 20, size=4)     else:         customer_input = list()         customer_input.append(input(＂请输入第一个数字:＂))         customer_input.append(input(＂请输入第二个数字:＂))         customer_input.append(input(＂请输入第三个数字:＂))         customer_input.append(input(＂请输入第四个数字:＂))     task = Solver()     answer = task.solution(customer_input)     if len(answer) == 0:         print(＂No solutions＂)     else:         for a in answer:             print(a)