递归 | HJ67 24点游戏算法

# 最优解
import sys
def func(nums, tar):
    if len(nums) == 1: return nums[0] == tar
    # 注意各种计算顺序都要考虑
    for i in range(len(nums)):
        nums = nums[1:] + [nums[0]]
        if func(nums[1:], tar+nums[0]) or func(nums[1:], tar-nums[0]) \
            or func(nums[1:], tar*nums[0]) or func(nums[1:], tar/nums[0]):
            return True
    return False
     
for line in sys.stdin:
    nums = list(map(int, line.strip().split()))
    print(str(func(nums, 24)).lower())


# 我的代码
def func(left, nums, oprs):
    if not left:
        n1, n2, n3, n4 = nums[0], nums[1], nums[2], nums[3]
        opr1, opr2, opr3 = oprs[0], oprs[1], oprs[2]
        exp1 = eval(f'{n1}{opr1}{n2}')
        exp2 = eval(f'{exp1}{opr2}{n3}')
        exp3 = f'{exp2}{opr3}{n4}'
        if eval(exp3) == 24:
            res.append(exp3)
        return
    for i in range(len(left)):
        func(left[:i]+left[i+1:], nums+[left[i]], oprs+['+'])
        func(left[:i]+left[i+1:], nums+[left[i]], oprs+['-'])
        func(left[:i]+left[i+1:], nums+[left[i]], oprs+['*'])
        func(left[:i]+left[i+1:], nums+[left[i]], oprs+['/'])

while True:
    try:
        n = list(map(int, input().split()))
        res = []
        func(n, [], [])
        if res:
            print('true')
        else:
            print('false')
    except:
        break

用时：40min