38、计算n的阶乘

题目
计算n的阶乘

解法一
使用递归解决：

#!/usr/bin/python
# -*- coding:UTF-8 -*-


class Factorial(object):
    def factorial(self, n):
        if n < 0:
            return False
        if n == 0 or n == 1:
            return 1
        if n > 1:
            return n * self.factorial(n - 1)


if __name__ == '__main__':
    n = 5
    ft = Factorial()
    result = ft.factorial(n)
    print result

解法二
使用reduce和 lambda解决

#!/usr/bin/python
# -*- coding:UTF-8 -*-


class Factorial(object):
    def factorial(self, n):
        return reduce(lambda x, y: x * y, range(1, n + 1))


if __name__ == '__main__':
    n = 3
    ft = Factorial()
    result = ft.factorial(n)
    print result