归档:2012年5月月

[ACM_SMU_1104]最优矩阵连乘积

杰拉斯 杰拉斯 | 时间:2012-05-24, Thu | 11,393 views
编程算法 

最优矩阵连乘积

Accepted: 10 Total Submit: 18
Time Limit: 1000ms Memony Limit: 32768KB

Description

在科学计算中经常要计算矩阵的乘积。矩阵A和B可乘的条件是矩阵A的列数等于矩阵B的行数。若A是一个p×q的矩阵,B是一个q×r的矩阵,则其乘积C=AB是一个p×r的矩阵。其标准计算公式为:

最优矩阵连乘

由该公式知计算C=AB总共需要pqr次的数乘。

为了说明在计算矩阵连乘积时加括号方式对整个计算量的影响,我们来看一个计算3个矩阵{A1,A2,A3}的连乘积的例子。设这3个矩阵的维数分别为10×100,100×5和5×50。若按第一种加括号方式((A1A2)A3)来计算,总共需要10×100×5+10×5×50=7500次的数乘。若按第二种加括号方式(A1(A2A3))来计算,则需要的数乘次数为100×5×50+10×100×50=75000。第二种加括号方式的计算量是第一种加括号方式的计算量的10倍。由此可见,在计算矩阵连乘积时,加括号方式,即计算次序对计算量有很大影响。

于是,人们自然会提出矩阵连乘积的最优计算次序问题,即对于给定的相继n个矩阵{A1,A2,…,An}(其中Ai的维数为pi-1×pi ,i=1,2,…,n),如何确定计算矩阵连乘积A1A2…An的一个计算次序(完全加括号方式),使得依此次序计算矩阵连乘积需要的数乘次数最少。

Input

有若干种案例,每种两行,第一行是一个非负整数n表示矩阵的个数,n=0表示结束。接着有n行,每行两个正整数,表示矩阵的维数。

Ouput
对应输出最小的乘法次数。

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[ACM实验六]ACM程序设计基础(4)

杰拉斯 杰拉斯 | 时间:2012-05-22, Tue | 15,875 views
编程算法 

实验项目:ACM程序设计基础(4)
实验目的:掌握C++程序设计基础。
实验要求:使用VC++6.0实现实验要求。
实验内容:

1.设有n个活动的集合E={1,2,…n},其中每个活动都要求使用同一资源,如演讲会场等,而在同一时间内只有一个活动能使用这一资源。每个活动i都有一个要求使用该资源的起始时间Si和一个结束时间Fi,且Si<Fi,求出最多可以安排多少个活动使用该资源,并给出一个安排方案,如:

i 1 2 3 4 5 6 7 8 9 10 11
Si 12 5 0 3 8 5 2 8 3 6 1
Fi 14 7 6 5 12 9 13 11 8 10 4

最多安排的资源个数为4,安排方案为:11 2 8 1
Sample Input
11 12 14 5 7 0 6 3 5 8 12 5 9 2 13 8 11 3 8 6 10 1 4
Sample Output
11 2 8 1 (4)
2.用KMP算法实现实验,输入两个只包含小写字母的字符串,判断第二个字符串是否是第一个字符串的子串,是则输出第二字符串在第一个字符串的起始位置,不是则输出NO。例如:
输入:abedsadfdseg
dsa
输出:4
3. Crashing Balloon问题,见Crashing Balloon

(阅读全文…)

[ACM_ZOJ_1003]Crashing Balloon

杰拉斯 杰拉斯 | 时间:2012-05-22, Tue | 22,130 views
编程算法 

Crashing Balloon

Time Limit: 2 Seconds Memory Limit: 65536 KB

Description

On every June 1st, the Children's Day, there will be a game named "crashing balloon" on TV. The rule is very simple. On the ground there are 100 labeled balloons, with the numbers 1 to 100. After the referee shouts "Let's go!" the two players, who each starts with a score of "1", race to crash the balloons by their feet and, at the same time, multiply their scores by the numbers written on the balloons they crash. After a minute, the little audiences are allowed to take the remaining balloons away, and each contestant reports his\her score, the product of the numbers on the balloons he\she's crashed. The unofficial winner is the player who announced the highest score.

Inevitably, though, disputes arise, and so the official winner is not determined until the disputes are resolved. The player who claims the lower score is entitled to challenge his\her opponent's score. The player with the lower score is presumed to have told the truth, because if he\she were to lie about his\her score, he\she would surely come up with a bigger better lie. The challenge is upheld if the player with the higher score has a score that cannot be achieved with balloons not crashed by the challenging player. So, if the challenge is successful, the player claiming the lower score wins.

So, for example, if one player claims 343 points and the other claims 49, then clearly the first player is lying; the only way to score 343 is by crashing balloons labeled 7 and 49, and the only way to score 49 is by crashing a balloon labeled 49. Since each of two scores requires crashing the balloon labeled 49, the one claiming 343 points is presumed to be lying.

On the other hand, if one player claims 162 points and the other claims 81, it is possible for both to be telling the truth (e.g. one crashes balloons 2, 3 and 27, while the other crashes balloon 81), so the challenge would not be upheld.

By the way, if the challenger made a mistake on calculating his/her score, then the challenge would not be upheld. For example, if one player claims 10001 points and the other claims 10003, then clearly none of them are telling the truth. In this case, the challenge would not be upheld.

Unfortunately, anyone who is willing to referee a game of crashing balloon is likely to get over-excited in the hot atmosphere that he\she could not reasonably be expected to perform the intricate calculations that refereeing requires. Hence the need for you, sober programmer, to provide a software solution.

Input

Pairs of unequal, positive numbers, with each pair on a single line, that are claimed scores from a game of crashing balloon.

Output

Numbers, one to a line, that are the winning scores, assuming that the player with the lower score always challenges the outcome.

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谈谈CSS Sprites技术及其优化

杰拉斯 杰拉斯 | 时间:2012-05-17, Thu | 9,218 views
前端开发 

很久之前就想具体地研究一下CSS Sprites了,今儿个看到微博UDC的这篇文章,赶紧转来,已经很晚了,留待有空研究= =。。

CSS Sprites 技术对于广大的前端工程师来说应该是一点也不陌生。这个被国内开发者昵称为CSS精灵 CSS雪碧的家伙到底解决了什么问题,我们又怎样合理使用这个技术呢?下面让我们详细的聊聊。

谈谈CSS Sprites技术及其优化

在大家还在拨号上网的“远古时期”,由于网速的限制,页面开发者都喜欢把网页里面的图片字节数控制的非常小,往往在一个图片文件夹里散落着n多的小碎图。随着网络技术的发展,网速的提升,大家越来越重视页面的加载速度,页面效率问题,过去的那些小图便成为了前端开发者的眼中钉,因为每加载一张图片都会产生一次浏览器请求数,发起的请求数越多那么页面加载的速度也越慢。还有当页面加载时,图片一个个的零星显示,鼠标经过时候背景闪白等也都是我们不能忍受的。于是乎将页面中的背景图整合到一起,利用“background-image”,“background- repeat”,“background-position”的组合进行背景定位的技术被广泛使用与了页面构建中,这就是CSS Sprites。当然CSS Sprites技术也存在着维护不便,内存占用大等等的缺点。

好了,如果我只说这些,那么这篇文章就有点太水了。前面那些只是对CSS Sprites技术的一个普及。作为一个开发者我们应该对它有一个更全面的认识,挖掘深度内容,这样才能有利于我们效率开发,团队协作。

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[日记一篇]无名思绪

杰拉斯 杰拉斯 | 时间:2012-05-11, Fri | 27,775 views
心路历程 

明天要去当一个小小颁奖仪式的主持人,其实本身没有多少做主持人的经验,似乎唯一的一次就是部门第一次面试通过见面会了,虽不感觉紧张,心里还是有些小小的忐忑,但无论如何,这未尝不是一次很好的锻炼机会,也未尝不是对我的一种肯定,从高三一个认识班里同学不超过五个的人到现在,不到两年的时间,其中付出的努力绝对不少,但这一切我想都是值得的,因为我看到了我的进步,我想要变的优秀,我会做到的。

——于2012-5-11凌晨2:41