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上下文無關文法（Context-Free Grammar, CFG）是一個4元組G=(V, T, S, P)，其中，V和T是不相交的有限集，S∈V，P是一組有限的產生式規則集，形如A→α，其中A∈V，且α∈(V∪T)*。V的元素稱為非終結符，T的元素稱為終結符，S是一個特殊的非終結符，稱為文法開始符。
設G=(V, T, S, P)是一個CFG，則G產生的語言是所有可由G產生的字符串組成的集合，即L(G)={x∈T* | Sx}。一個語言L是上下文無關語言（Context-Free Language, CFL），當且僅當存在一個CFG G，使得L=L(G)。 *⇒
例如，設文法G：S→AB
A→aA|a
B→bB|b
則L(G)={a^nb^m | n,m>=1}
其中非終結符都是大寫字母，開始符都是S，終結符都是小寫字母。
標簽：
Context-Free
Grammar
CFG
上傳時間：
2013-12-10
上傳用戶：gaojiao1999
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We have a group of N items (represented by integers from 1 to N), and we know that there is some total order defined for these items. You may assume that no two elements will be equal (for all a, b: a<b or b<a). However, it is expensive to compare two items. Your task is to make a number of comparisons, and then output the sorted order. The cost of determining if a < b is given by the bth integer of element a of costs (space delimited), which is the same as the ath integer of element b. Naturally, you will be judged on the total cost of the comparisons you make before outputting the sorted order. If your order is incorrect, you will receive a 0. Otherwise, your score will be opt/cost, where opt is the best cost anyone has achieved and cost is the total cost of the comparisons you make (so your score for a test case will be between 0 and 1). Your score for the problem will simply be the sum of your scores for the individual test cases.
標簽：
represented
integers
group
items
上傳時間：
2016-01-17
上傳用戶：jeffery
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(1) 、用下述兩條具體規則和規則形式實現.設大寫字母表示魔王語言的詞匯 小寫字母表示人的語言詞匯 希臘字母表示可以用大寫字母或小寫字母代換的變量.魔王語言可含人的詞匯.
(2) 、B→tAdA A→sae
(3) 、將魔王語言B(ehnxgz)B解釋成人的語言.每個字母對應下列的語言.
標簽：
字母
tAdA
語言
詞匯
上傳時間：
2013-12-30
上傳用戶：ayfeixiao
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1.有三根桿子A,B,C。A桿上有若干碟子
2.每次移動一塊碟子,小的只能疊在大的上面
3.把所有碟子從A桿全部移到C桿上
經過研究發現，漢諾塔的破解很簡單，就是按照移動規則向一個方向移動金片：
如3階漢諾塔的移動：A→C,A→B,C→B,A→C,B→A,B→C,A→C
此外，漢諾塔問題也是程序設計中的經典遞歸問題
標簽：
移動
發現
上傳時間：
2016-07-25
上傳用戶：gxrui1991
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A stability analysis is presented for staggered schemes for the governing equations of compressible flow. The
method is based on Fourier analysis. The approximate nature of pressure-correction solution methods is taken into
account. 2001 IMACS. Published by Elsevier Science B.V. All rights reserved
標簽：
compressible
stability
for
equations
上傳時間：
2016-12-02
上傳用戶：yph853211
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1. 下列說法正確的是 （ ）
A. Java語言不區分大小寫
B. Java程序以類為基本單位
C. JVM為Java虛擬機JVM的英文縮寫
D. 運行Java程序需要先安裝JDK
2. 下列說法中錯誤的是 ( )
A. Java語言是編譯執行的
B. Java中使用了多進程技術
C. Java的單行注視以//開頭
D. Java語言具有很高的安全性
3. 下面不屬于Java語言特點的一項是( )
A. 安全性
B. 分布式
C. 移植性
D. 編譯執行
4. 下列語句中，正確的項是 ( )
A . int $e,a,b=10
B. char c,d=’a’
C. float e=0.0d
D. double c=0.0f
標簽：
Java
A.
B.
C.
上傳時間：
2017-01-04
上傳用戶：netwolf
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數字運算，判斷一個數是否接近素數
A Niven number is a number such that the sum of its digits divides itself. For example, 111 is a Niven number because the sum of its digits is 3, which divides 111. We can also specify a number in another base b, and a number in base b is a Niven number if the sum of its digits divides its value.
Given b (2 <= b <= 10) and a number in base b, determine whether it is a Niven number or not.
Input
Each line of input contains the base b, followed by a string of digits representing a positive integer in that base. There are no leading zeroes. The input is terminated by a line consisting of 0 alone.
Output
For each case, print "yes" on a line if the given number is a Niven number, and "no" otherwise.
Sample Input
10 111
2 110
10 123
6 1000
8 2314
0
Sample Output
yes
yes
no
yes
no
標簽：
數字
運算
上傳時間：
2015-05-21
上傳用戶：daguda
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源代碼\用動態規劃算法計算序列關系個數
用關系"<"和"="將3個數a，b，c依次序排列時，有13種不同的序列關系：
a=b=c,a=b<c,a<b=v,a<b<c,a<c<b
a=c<b,b<a=c,b<a<c,b<c<a,b=c<a
c<a=b,c<a<b,c<b<a
若要將n個數依序列，設計一個動態規劃算法，計算出有多少種不同的序列關系，
要求算法只占用O(n),只耗時O(n*n).
標簽：
lt
源代碼
動態規劃
序列
上傳時間：
2013-12-26
上傳用戶：siguazgb
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TinyLogin is a suite of tiny Unix utilities for handling logging into,
being authenticated by, changing one s password for, and otherwise
maintaining users and groups on an embedded system. It also provides
shadow password support to enhance system security. TinyLogin is, as the
name implies, very small, and makes an excellent complement to BusyBox
on an embedded System. It can be used without BusyBox, of course, but I
envision them being used together most of the time.
標簽：
authenticated
TinyLogin
utilities
handling
上傳時間：
2016-01-30
上傳用戶：253189838
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The XML Toolbox converts MATLAB data types (such as double, char, struct, complex, sparse, logical) of any level of nesting to XML format and vice versa.
For example,
>> project.name = MyProject
>> project.id = 1234
>> project.param.a = 3.1415
>> project.param.b = 42
becomes with str=xml_format(project, off )
"<project>
<name>MyProject</name>
<id>1234</id>
<param>
<a>3.1415</a>
<b>42</b>
</param>
</project>"
On the other hand, if an XML string XStr is given, this can be converted easily to a MATLAB data type or structure V with the command V=xml_parse(XStr).
標簽：
converts
Toolbox
complex
logical
上傳時間：
2016-02-12
上傳用戶：a673761058
