zoukankan      html  css  js  c++  java
  • 【leetcode】1006. Clumsy Factorial

    题目如下:

    Normally, the factorial of a positive integer n is the product of all positive integers less than or equal to n.  For example, factorial(10) = 10 * 9 * 8 * 7 * 6 * 5 * 4 * 3 * 2 * 1.

    We instead make a clumsy factorial: using the integers in decreasing order, we swap out the multiply operations for a fixed rotation of operations: multiply (*), divide (/), add (+) and subtract (-) in this order.

    For example, clumsy(10) = 10 * 9 / 8 + 7 - 6 * 5 / 4 + 3 - 2 * 1.  However, these operations are still applied using the usual order of operations of arithmetic: we do all multiplication and division steps before any addition or subtraction steps, and multiplication and division steps are processed left to right.

    Additionally, the division that we use is floor division such that 10 * 9 / 8 equals 11.  This guarantees the result is an integer.

    Implement the clumsy function as defined above: given an integer N, it returns the clumsy factorial of N.

    Example 1:

    Input: 4
    Output: 7
    Explanation: 7 = 4 * 3 / 2 + 1
    

    Example 2:

    Input: 10
    Output: 12
    Explanation: 12 = 10 * 9 / 8 + 7 - 6 * 5 / 4 + 3 - 2 * 1
    

    Note:

    1. 1 <= N <= 10000
    2. -2^31 <= answer <= 2^31 - 1  (The answer is guaranteed to fit within a 32-bit integer.)

    解题思路:把等式拆分成两部分,一是N*(N-1)/(N-2),二是加上N+3。

    代码如下:

    class Solution(object):
        def clumsy(self, N):
            """
            :type N: int
            :rtype: int
            """
            add = 0
            other = None
            while N > 0:
                tmp = N
                if N - 1 > 0:
                    tmp *= (N-1)
                if N - 2 > 0:
                    tmp /= (N-2)
                if N - 3 > 0:
                    add += (N-3)
                if other == None:
                    other = tmp
                else:
                    other -= tmp
                N -= 4
            return other + add
  • 相关阅读:
    非域账户如何连接SQL Server Analysis Service
    Ranet.UILibrary.OLAP
    给Silverlight项目Ranet.UILibrary.OLAP添加客户端调试功能
    编译及安装QCA类库
    关于软件生态环境
    Windows7中操作mysql数据库
    介绍自己
    VS2008技巧收集
    .NET开发不可错过的25款必备工具
    如何做搜索引擎优化(SEO)
  • 原文地址:https://www.cnblogs.com/seyjs/p/10508819.html
Copyright © 2011-2022 走看看