题解 | #24点游戏算法#

import itertools


def cal(strings):
    nums = []
    for c in strings:
        if c.isdigit():
            if c == '0':
                nums.pop()
                nums.append(10)
            else:
                nums.append(int(c))
        else:
            r = str(nums.pop())
            l = str(nums.pop())
            nums.append(eval(l + c + r))
    return nums.pop()


def shizi(num, ans, index):
    if ans:
        return True
    for opt1 in '+-*/':
        houzhui1 = num.copy()
        houzhui1.insert(index[0], opt1)
        for opt2 in '+-*/':
            houzhui2 = houzhui1.copy()
            houzhui2.insert(index[1], opt2)
            for opt3 in '+-*/':
                houzhui3 = houzhui2.copy()
                houzhui3.insert(index[2], opt3)
                try:
                    if cal(houzhui3) == 24:
                        return True
                except:
                    continue
    return False


ans = False
num = list(input().split())
nums = list(itertools.permutations(num))
for num in nums:
    num = list(num)
    ans = shizi(num, ans, [2, 5, 6])
    ans = shizi(num, ans, [4, 5, 6])
    ans = shizi(num, ans, [3, 5, 6])
    ans = shizi(num, ans, [3, 4, 6])
    ans = shizi(num, ans, [2, 4, 6])
if ans:
    print('true')
else:
    print('false')

思路很简单，由于考虑括号，直接转为后缀表达式，就不用考虑括号了，4个数的后缀表达式，只需要加3个符号，位置的可能性只有5种