算法题：数字翻译

September 21, 2014

###问题描述

给定一个数字串将其翻译成字母组，其中1->a, 2->b,…, 26->z，另外0x（x不等于0）相当于x. 例如输入12259，可以翻译成lyi，abbei， lbei,avei或者abyi。输入一个数字串，判断其能否翻译成字母组，若能打印所有可能翻译成的字母组。

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Android animation开发笔记

June 8, 2014

最近的工作涉及到Android的animation开发，学到了一些之前没有注意到的知识点，作个记录。

fillEnable、fillBefore和fillAfter

Animation的fillBefore和fillAfter属性分别用来控制动画开始之前或者播放完毕时是否将transformation作用到视图上，默认情况下它们的值分别为true和false。如果在xml文件中将fillAfter设置为true，那么在动画播放完毕后，视图会停留在动画的最后一个状态，这种效果是符合预期的。但是如果将fillBefore设置为false同时设置了startOffset，就会发现在动画真正开始前视图就已经处于动画的第一个状态，也就意味着fillBefore＝false不起作用。按照官方文档的说明，fillBefore＝false 只有在fillEnable被设置为true的情况下才会起作用。为何会出现这种奇怪的问题？从源代码中可以找到答案。以下是Animation的getTransformation函数中的几行代码：

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Code Jam 2014之Cookie Clicker Alpha

April 13, 2014

Problem：

In this problem, you start with 0 cookies. You gain cookies at a rate of 
2 cookies per second, by clicking on a giant cookie. Any time you have 
at least C cookies, you can buy a cookie farm. Every time you buy a 
cookie farm, it costs you C cookies and gives you an extra F cookies 
per second.

Once you have X cookies that you haven't spent on farms, you win! 
Figure out how long it will take you to win if you use the best 
possible strategy.

Example

Suppose C=500.0, F=4.0 and X=2000.0. Here's how the best 
possible strategy plays out:

 1. You start with 0 cookies, but producing 2 cookies per second.
 2. After 250 seconds, you will have C=500 cookies and can buy 
    a farm that produces F=4 cookies per second.
 3. After buying the farm, you have 0 cookies, and your total 
    cookie production is 6 cookies per second.
 4. The next farm will cost 500 cookies, which you can buy 
    after about 83.3333333 seconds.
 5. After buying your second farm, you have 0 cookies, and your 
    total cookie production is 10 cookies per second.
 6. Another farm will cost 500 cookies, which you can buy after
    50 seconds.
 7. After buying your third farm, you have 0 cookies, and your 
    total cookie production is 14 cookies per second.
 8. Another farm would cost 500 cookies, but it actually makes 
    sense not to buy it: instead you can just wait until you have 
    X=2000 cookies, which takes about 142.8571429 seconds.

Total time: 250 + 83.3333333 + 50 + 142.8571429 = 526.1904762 
seconds.

Notice that you get cookies continuously: so 0.1 seconds after 
the game starts you'll have 0.2 cookies, and π seconds after 
the game starts you'll have 2π cookies.

My solution:

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Objective-C学习之property VS instance variable

February 26, 2014

Objective-C提供两种方式来声明一个类（interface）中的成员变量：property以及instance variable。

property

如果将成员变量声明成property，编译器会自动生成相应的getter和setter函数，同时还会生成一个对应的instance variable。例如，给一个类XYZClass声明一个property member：
```
@interface XYZClass : NSObject

@property id member;

@end
```
那么在类的方法中可以通过以下三种方式访问member：
```
// 通过getter方法
[self member]
// 通过点方法
self.member
// 通过对应的instance variable
_member
```
类的property对外是公开的，在非本类的代码中可以通过getter以及点方法访问property。另外，Objective-C允许为property定义各种属性，不同的属性赋予了property不同的特性，参考http://rypress.com/tutorials/objective-c/properties.html

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第0篇

January 24, 2014

这不是一篇正式的博客。就像每一本书都有一个序言，总觉得在正式开始之前要写点什么，因此有了这篇博客。即将告别学生生涯，但是学习不能停，所以我把博客的标题设为“学无止境”。有时觉得写博客是件麻烦事，因为要把杂乱的资料整理成一篇有条理的文章既费时又费力。不过，把写博客当成总结和再次学习的过程也不失为一种乐趣。

先设定接下来一段时间的学习目标：

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