使用加、减、乘、除4种运算以及括号把给出的4 个小于10的正整数连接起来得到一个表达式，并且使得所得的这个表达式的结果等于24
这里加、减、乘、除4种运算以及括号的运算结果与运算优先级跟平常定义一致
number = [0] * 4
result = [‘‘] * 4
def PointsGame(n):
if n == 1:
return abs(number[0] - 24) < 1e-6
for i in range(n):
for j in range(i+1,n):
a, b = number[i], number[j]
number[j] = number[n-1]
charA, charB = result[i],result[j]
result[j] = result[n-1]
result[i] = ‘(‘ + charA + ‘+‘ + charB + ‘)‘
number[i] = a + b
if PointsGame(n-1):
return True
result[i] = ‘(‘ + charA + ‘-‘ + charB + ‘)‘
number[i] = a - b
if PointsGame(n-1):
return True
result[i] = ‘(‘ + charA + ‘*‘ + charB + ‘)‘
number[i] = a * b
if PointsGame(n-1):
return True
if b != 0:
result[i] = ‘(‘ + charA + ‘/‘ + charB + ‘)‘
number[i] = a / b
if PointsGame(n-1):
return True
if a != 0:
result[i] = ‘(‘ + charB + ‘/‘ + charA + ‘)‘
number[i] = b / a
if PointsGame(n-1):
return True
number[i], number[j] = a, b
result[i], result[j] = charA ,charB
return False
if __name__ == ‘__main__‘:
for i in range(4):
x = input()
number[i] = int(x)
result[i] = x
if PointsGame(4):
print(‘YES‘)
print(result[0])
else:
print(‘NO‘)
原文：https://www.cnblogs.com/cnn-ljc/p/12711771.html