题解 | #24点游戏算法#

import sys
ops = ["+", "-", "*", "/"]

# 从四个数中任意挑俩数，计算结果放回去，变成仨数
# 从三个数中任意挑俩数，计算结果放回去，变成俩数
# 最后俩数执行运算
def cal(a, b, op):
    if op == "+":
        return a+b
    elif op == "-":
        return a-b
    elif op == "*":
        return a*b
    elif op == "/":
        if b == 0:
            return 0
        else:
            return a/b

def dfs(nums):
    n = len(nums)
    if n == 1:
        return nums[0]
    
    for i in range(n):
        for j in range(n):
            if i != j:
                for op in ops:
					# 首先挑出两个数进行计算
                    nums_copy = [cal(nums[i], nums[j], op)]
                    for k in range(n):
                        if k != i and k != j:
                            nums_copy.append(nums[k])
					# 计算完毕重新进入计算
                    if dfs(nums_copy) == 24:
                        return 24
    return 0
                        
for line in sys.stdin:
    nums = list(map(int, line.strip().split(" ")))
    print("true" if dfs(nums) == 24 else "false")