24点问题

屈老师

from itertools import permutations, product
from time import sleep
from random import randint

def calculate_postfix(expression):
    """
    计算后缀表达式的值
    """
    stack = []
    for token in expression:
        if isinstance(token, (int, float)):  # 数字入栈
            stack.append(float(token))
        else:  # 操作符出栈计算
            b = stack.pop()
            a = stack.pop()
            if token == '+':
                stack.append(a + b)
            elif token == '-':
                stack.append(a - b)
            elif token == '*':
                stack.append(a * b)
            elif token == '/':
                if abs(b) < 1e-6:  # 避免除以零
                    return None
                stack.append(a / b)
    return stack[0] if stack else None

def calculate_result(expression):
    """
    计算后缀表达式的值
    """
    stack = []
    for token in expression:
        if isinstance(token, (int, float)):  # 数字入栈
            stack.append(int(token))
        else:  # 操作符出栈计算
            b = stack.pop()
            a = stack.pop()
            if token == '+':
                stack.append(a + b)
                print(a, token, b, '=',a+b)
            elif token == '-':
                stack.append(a - b)
                print(a, token, b, '=',a-b)
            elif token == '*':
                stack.append(a * b)
                print(a, token, b, '=',a*b)
            elif token == '/':
                if abs(b) < 1e-6:  # 避免除以零
                    return None
                stack.append(a / b)
                print(a, token, b, '=',a/b)
    print('结果:',stack[0])
    return


def can_make_24(nums):
    """
    判断是否可以通过排列和运算符组合得到 24 点
    """
    TARGET = 24
    EPSILON = 1e-6
    operators = ['+', '-', '*', '/']

    # 枚举所有数字的排列
    for num_perm in permutations(nums):
        # 枚举所有运算符的排列
        for ops in product(operators, repeat=3):
            # 构造所有后缀表达式的可能性
            postfix_expressions = [
                [num_perm[0], num_perm[1], ops[0], num_perm[2], ops[1], num_perm[3], ops[2]],
                [num_perm[0], num_perm[1], num_perm[2], ops[0], ops[1], num_perm[3], ops[2]],
                [num_perm[0], num_perm[1], ops[0], num_perm[2], num_perm[3], ops[1], ops[2]],
                [num_perm[0], num_perm[1], num_perm[2], ops[0], num_perm[3], ops[1], ops[2]]
            ]

            # 计算每个后缀表达式
            for postfix in postfix_expressions:
                result = calculate_postfix(postfix)
                if result is not None and abs(result - TARGET) < EPSILON:
                    print("表达式:", postfix)
                    calculate_result(postfix)
                    return True  # 找到满足条件的解即可返回 True

    return False  # 遍历所有组合后仍未找到解
def generate_num():
    nums = [randint(1,25) for _ in range(4)]
    print(nums)
    return nums

# 测试用例
nums=generate_num()
sleep(10)
if can_make_24(nums):
    print("可以拼出 24 点！")
else:
    print("无法拼出 24 点！")