再见凤凰花开: 学习

Jialin 的个人资料再见凤凰花开照片日志列表

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2009/10/9

一个题目 - 剑客坐火车

一个剑客，有一把长1.5米的剑；他去坐火车；乘务员不允许把剑作为随行行李
带上火车，所以只能把剑作为托运行李了。
可是火车又有规定，任何托运行李最长的一条边不能长于1米。
这个剑客该怎么办才能坐火车呢？

2009/10/7

一个题目

人口普查统计员到了一家人门口，问妇女：你家有几个小孩，分别多大？
妇女说：我家3个小孩，他们的年龄都是整数，而且他们年龄的积等于36.
人口统计员说：这个信息不够。
妇女说：就算我告诉你他们年龄加起来的和，你也还是没法子确定他们各个的年龄的。
人口统计与说：能不能再多给一些信息？
妇女说：我最大的那一个孩子特别喜欢狗。

根据这些信息，人口统计员可以推算出三个孩子各自的年龄吗？

2009/1/5

看新闻，学英语

最近看财经类的新闻，学了不少词，都是不太好的

dismal (dismal economy)

abysmal

bleak (bleak sales ..)

woe (automaker woes)

pledge (Obama pledged to save the economy)

我想，等那天经济好转的时候，也一定要多看新闻，那就可以把这次词的反义词都学会了

2008/9/25

crouton

crouton - ['kru:tɔn] - 这种小面包叫croutons

2008/9/23

看图学单词——毛豆

Edamame

2008/9/7

Suppose the positive number n is odd. First Alex writes the number 1, 2, ..., 2n on the blackboard. Then he picks any two numbers a, b, erase them, and writes, instead, |a-b|. Prove that an odd number will remain at the end.

Solution 1:

Suppose S is the sum of all numbers still on the blackboard. Each step, reduce S by 2min(a,b), which is an even number.

So the parity of S is an invarant.

Initially S = 1+2+...+2n = (1+2n)n, an odd number; so during the whole reduction process, S will stay an odd number.

So at the end, when there is only one number left, it must be an odd number.

Solution 2:

Initially, there are n odd numbers and n even numbers in 1, 2, ..., 2n;

Suppost X is the number of odd numbers on the blackboard, initially X = n , an odd number.

We suspect the parity of X will stay the same (the invariant).

in each step, one of the following 4 cases can happen,

(1) if both a and b is even, then |a-b| is even -> erasing a, b and adding |a-b| will not change the parity of X;

(2) if both a and b is odd, then |a-b| is even -> X-2 is still odd

(3) if a is even and b is odd, then |a-b| is odd -> X-1+1 is still odd

(4) if a is odd and b is even, then |a-b| is odd -> X-1+1 is still odd

so X is always odd.

so at the end, an odd number remains.

2008/9/1

一个英文单词——Xing

在美国，在路上，经常看到这样的交通牌：

第二个牌中的PED是pedestrian（行人）的前3个字母，这里的Xing字，一直让我不清楚，还查了字典，都没有这个字，难道是中文行人的“行”字的拼音？有点不解，一直都忘了问老外这回事。

最近在Wyoming那边山里看到一个拍，写着Deer X-ing的，我才想明白了，原来Xing就是X-ing，就是Crossing（过路）的意思，因为X（交叉）在英文里是Cross，所以老外就很懒的用Xing来代替Crossing了。

2008/6/14

The King's English General Principles

摘自The King's English by H.W. Fowler & F.G.Fowler

Any one who wishes to become a good writer should endeavour,
before he allows himself to be tempted by the more showy qualities,
to be direct, simple, brief, vigorous, and lucid.

This general principle may be translated into practical rules in the domain
of vocabulary as follows:
Prefer the familiar word to the far-fetched.
Prefer the concrete word to the abstract.
Prefer the single word to the circumlocution.
Prefer the short word to the long.
...

觉得大体上不但是适用于英语，同样也适用于汉语。

2007/8/8