python计算24点

输入4个数字, 输出所有用加减乘除结果为24的表达式. 代码如下:

def isEqual(num1, num2):

return abs(num1 - num2) < 1e-5;

# End of isEqual().

def expressionsFromExpOpSeq(expSeq, opSeq):

assert(len(expSeq) == len(opSeq) + 1)

if 1 == len(expSeq):

yield expSeq[0]

return

# End of if.

for idx in range(len(opSeq)):

newExp = "(%s %s %s)" % (

expSeq[idx], opSeq[idx], expSeq[idx+1])

newExpSeq = expSeq[:idx] + [newExp] + expSeq[idx+2:]

newOpSeq = opSeq[:idx] + opSeq[idx+1:]

for exp in expressionsFromExpOpSeq(newExpSeq, newOpSeq):

yield exp

# End of for.

# End of expressionsFromExpOpSeq().

def expressionsFromExpSeq(expSeq):

for opSeq in selections("+-*/", len(expSeq) - 1):

for exp in expressionsFromExpOpSeq(expSeq, opSeq):

yield exp

# End of expressionsFromExpSeq().

def expressions(numList):

'''Generate expressions.

'''

if (0 == len(numList)): return;

for numPerm in permutations(numList):

expSeq = [str(n) for n in numPerm]

for exp in expressionsFromExpSeq(expSeq):

yield exp

# End of expressions().

numTuple=input("Please input 4 numbers to computer 24:(use ',' to divide them)")

numList=[float(i) for i in numTuple]

# numList = [1.0,4.0,5.0,6.0]

TARGET = 24.0

print("Your input is: %s" % numList)

for exp in expressions(numList):

try:

if isEqual(TARGET, eval(exp)):

print("%s = %s" % (exp, TARGET))

except ZeroDivisionError:

pass

# End of try.

# End of for.

其中计算排列组合的代码来自Cookbook:

# Recipe 19.15. Generating Permutations, Combinations, and Selections

def _combinators(_handle, items, n):

''' factored-out common structure of all following combinators '''

if n==0:

yield [ ]

return

for i, item in enumerate(items):

this_one = [ item ]

for cc in _combinators(_handle, _handle(items, i), n-1):

yield this_one + cc

def combinations(items, n):

''' take n distinct items, order matters '''

def skipIthItem(items, i):

return items[:i] + items[i+1:]

return _combinators(skipIthItem, items, n)

def selections(items, n):

''' take n (not necessarily distinct) items, order matters '''

def keepAllItems(items, i):

return items

return _combinators(keepAllItems, items, n)

def permutations(items):

''' take all items, order matters '''

return combinations(items, len(items))

示例:

Please input 4 numbers to computer 24:(use ',' to divide them)1,4,5,6

Your input is: [1.0, 4.0, 5.0, 6.0]

(4.0 / (1.0 - (5.0 / 6.0))) = 24.0

(6.0 / ((5.0 / 4.0) - 1.0)) = 24.0

也可以输入多个数字:

Please input 4 numbers to computer 24:(use ',' to divide them)2,3,4,5.5,6

Your input is: [2.0, 3.0, 4.0, 5.5, 6.0]

((2.0 - (3.0 / (4.0 - 5.5))) * 6.0) = 24.0

(2.0 * (3.0 - ((4.0 - 5.5) * 6.0))) = 24.0

((2.0 + (3.0 / (5.5 - 4.0))) * 6.0) = 24.0

......

参考:

* 一个 Lua 的凑24程序 ( http://blog.csdn.net/shell_picker/archive/2010/11/25/6034158.aspx )

* python 算24的题目 ( http://zhidao.baidu.com/question/207378450.html )