LaTeX 算法流程代码 LaTeX Algorithms guide

LaTeX has several packages for typesetting algorithms in form of "pseudocode". They provide stylistic enhancements over a uniform style (i.e., all in typewriter font) so that constructs such as loops or conditionals are visually separated from other text. The pseudocode is usually put in an algorithm environment. For typesetting real code, written in a real programming language, consider the listings package described in Source Code Listings.

Typesetting[edit]

There are four notable packages algorithmic, algorithm2e, algorithmicx, and program,

Typesetting using the `algorithmic` package[edit]

The algorithmic package uses a different set of commands than the algorithmicx package. This is not compatible with revtex4-1. Basic commands are:

 STATE <text>
 IF{<condition>} STATE {<text>} ELSE STATE{<text>} ENDIF
 IF{<condition>} STATE {<text>} ELSIF{<condition>} STATE{<text>} ENDIF
 FOR{<condition>} STATE {<text>} ENDFOR
 FOR{<condition> TO <condition> } STATE {<text>} ENDFOR
 FORALL{<condition>} STATE{<text>} ENDFOR
 WHILE{<condition>} STATE{<text>} ENDWHILE
 REPEAT STATE{<text>} UNTIL{<condition>}
 LOOP STATE{<text>} ENDLOOP
 REQUIRE <text>
 ENSURE <text>
 RETURN <text>
 PRINT <text>
 COMMENT{<text>}
 AND, OR, XOR, NOT, TO, TRUE, FALSE

Complete documentation is listed at [2]. Most commands are similar to the algorithmicx equivalents, but with different capitalization. The package algorithms bundle at the ctan repository, dated 2009-08-24, describes both the algorithmic environment (for typesetting algorithms) and the algorithm floating wrapper (see below) which is designed to wrap around the algorithmic environment.

The algorithmic package is suggested for IEEE journals as it is a part of their default style sheet.^[1]

How to rename require/ensure to input/output:

重新定义require和ensure命令对应的关键字(此处将默认的Require/Ensure自定义为Input/Output)

floatname{algorithm}{Procedure}

enewcommand{algorithmicrequire}{	extbf{Input:}}

enewcommand{algorithmicensure}{	extbf{Output:}}

Typesetting using the `algorithm2e` package[edit]

The algorithm2e package (first released 1995, latest updated July 2017 according to the v5.0 manual) allows typesetting algorithms with a lot of customization. Like algorithmic, this package is also not compatible with Revtex-4.1.^[2]

Unlike algorithmic, algorithm2e provides a relatively huge number of customization options to the algorithm suiting to the needs of various users. The CTAN-manual provides a comprehensible list of examples and full set of controls.

Typically, the usage between egin{algorithm} and end{algorithm} would be
1. Declaring a set of keywords(to typeset as functions/operators), layout controls, caption, title, header text (which appears before the algorithm's main steps e.g.: Input,Output)
2. Writing the main steps of the algorithm, with each step ending with a ;
This may be taken in analogy with writing a latex-preamble before we start the actual document.

示例 1：

The package is loaded like

usepackage[]{algorithm2e}

and a simple example, taken from the v4.01 manual, is

egin{algorithm}[H]
 KwData{this text}
 KwResult{how to write algorithm with LaTeX2e }
 initialization;
 While{not at end of this document}{
  read current;
  eIf{understand}{
   go to next section;
   current section becomes this one;
   }{
   go back to the beginning of current section;
  }
 }
 caption{How to write algorithms}
end{algorithm}

which produces

More details are in the manual hosted on the ctan website.

示例 2：

egin{algorithm} %算法开始
caption{Sample algorithm} %算法的题目
label{alg1} %算法的标签
egin{algorithmic}[1] %此处的[1]控制一下算法中的每句前面都有标号
REQUIRE Text:Today is a good day. Variables:$u,v,w$. $G=(V,E)$ %输入条件(此处的REQUIRE默认关键字为Require，在上面已自定义为Input)
ENSURE Something... %输出结果(此处的ENSURE默认关键字为Ensure在上面已自定义为Output)
% if-then-else
IF{some condition is true}
STATE do some processing
ELSIF{some other condition is true}
STATE do some different processing
ELSE
STATE do the default actions
ENDIF
% for loop
FOR{$i=0$ to $10$}
STATE carry out some processing
ENDFOR
FORALL{$i$ such that $0leq ileq 10$}
STATE carry out some processing
ENDFOR
% while-loop
WHILE{some condition holds}
STATE carry out some processing
ENDWHILE
% repeat-until loop
REPEAT
STATE carry out some processing
UNTIL{some condition is met}
% infinite loop
LOOP
STATE this processing will be repeated forever
ENDLOOP

end{algorithmic}
end{algorithm}

输出：

Typesetting using the `algorithmicx` package[edit]

The algorithmicx package provides a number of popular constructs for algorithm designs. Put usepackage{algpseudocode} in the preamble to use the algorithmic environment to write algorithm pseudocode (egin{algorithmic}...end{algorithmic}). You might want to use the algorithm environment (usepackage{algorithm}) to wrap your algorithmic code in an algorithm environment (egin{algorithm}...end{algorithm}) to produce a floating environment with numbered algorithms.

The command egin{algorithmic} can be given the optional argument of a positive integer, which if given will cause line numbering to occur at multiples of that integer. E.g. egin{algorithmic}[5] will enter the algorithmic environment and number every fifth line.

Below is an example of typesetting a basic algorithm using the algorithmicx package (remember to add the usepackage{algpseudocode} statement to your document preamble):

egin{algorithmic}
If {$igeq maxval$}
    State $igets0$
Else
    If {$i+kleq maxval$}
        State $igets i+k$
    EndIf
EndIf
end{algorithmic}

The LaTeX source can be written to a format familiar to programmers so that it is easy to read. This will not, however, affect the final layout in the document.

Basic commands have the following syntax:

Statement (State causes a new line, can also be used in front of other commands)

State $xgets <value>$

Three forms of if-statements:

If{<condition>} <text> EndIf

If{<condition>} <text> Else <text> EndIf

If{<condition>} <text> ElsIf{<condition>} <text> Else <text> EndIf

The third form accepts as many ElsIf{} clauses as required. Note that it is ElsIf and not ElseIf.

Loops:

For{<condition>} <text> EndFor

ForAll{<condition>} <text> EndFor

While{<condition>} <text> EndWhile

Repeat <text> Until{<condition>}

Loop <text> EndLoop

Pre- and postcondition:

Require <text>

Ensure <text>

Functions

Function{<name>}{<params>} <body> EndFunction

Return <text>

Call{<name>}{<params>}

This command will usually be used in conjunction with a State command as follows:

Function{Increment}{$a$}
    State $a gets a+1$
    State Return $a$
EndFunction

Comments:

Comment{<text>}

Note to users who switched from the old algorithmic package: comments may be placed everywhere in the source; there are no limitations as in the old algorithmic package.

The algorithmicx package allows you to define your own environments.

To define blocks beginning with a starting command and ending with an ending command, use

algblock[<block>]{<start>}{<end>}

This defines two commands <start> and <end> which have no parameters. The text displayed by them is extbf{<start>} and extbf{<end>}.

With algblockdefx you can give the text to be output by the starting and ending command and the number of parameters for these commands. In the text the n-th parameter is referenced by #n.

algblockdefx[<block>]{<start>}{<end>}
    [<startparamcount>][<default value>]{<start text>}
    [<endparamcount>][<default value>]{<end text>}

Example:

algblock[Name]{Start}{End}
algblockdefx[NAME]{START}{END}%
    [2][Unknown]{Start #1(#2)}%
    {Ending}
algblockdefx[NAME]{}{OTHEREND}%
    [1]{Until (#1)}
egin{algorithmic}
Start
    Start
        START[One]{x}
        END
        START{0}
        OTHEREND{	exttt{True}}
    End
    Start
    End
End
end{algorithmic}

More advanced customization and other constructions are described in the algorithmicx manual: http://mirror.ctan.org/macros/latex/contrib/algorithmicx/algorithmicx.pdf

Typesetting using the `program` package[edit]

The program package provides macros for typesetting algorithms. Each line is set in math mode, so all the indentation and spacing is done automatically. The notation |variable_name| can be used within normal text, maths expressions or programs to indicate a variable name. Use origbar to get a normal | symbol in a program. The commands A, B, P, Q, R, S, T and typeset the corresponding bold letter with the next object as a subscript (eg S1 typesets {f S$_1$} etc). Primes work normally, eg S‘‘.

Below is an example of typesetting a basic algorithm using the program package (remember to add the usepackage{program} statement to your document preamble):

egin{program}
mbox{A fast exponentiation procedure:}
BEGIN \ %
  FOR i:=1 TO 10 STEP 1 DO
     |expt|(2,i); \ |newline|() OD %

comment{This text will be set flush to the right margin}
WHERE
PROC |expt|(x,n) BODY
          z:=1;
          DO IF n=0 THEN EXIT FI;
             DO IF |odd|(n) THEN EXIT FI;
COMMENT{This is a comment statement};
                n:=n/2; x:=x*x OD;
             { n>0 };
             n:=n-1; z:=z*x OD;
          |print|(z) ENDPROC
END
end{program}

The commands ( and ) are redefined to typeset an algorithm in a minipage, so an algorithm can appear as a single box in a formula. For example, to state that a particular action system is equivalent to a WHILE loop you can write:

[
(ACTIONS A:
        A EQIFB{} THENS{}; CALL A
ELSECALL Z FIQE
ENDACTIONS)
EQT
(WHILEB{} DOS{} OD)
]

Dijkstra conditionals and loops:

egin{program}
IF x = 1 AR y:=y+1
BAR x = 2 AR y:=y^2
utdots
BAR x = n AR y:=displaystylesum_{i=1}^n y_i FI

DO 2 origbar x AND x>0 AR x:= x/2
BAR NOT 2 origbar x AR x:= modbar{x+3} OD
end{program}

Loops with multiple exits:

egin{program}
DO DO IF B1 THEN EXIT FI;
        S1;
        IF B2 THEN EXIT(2) FI OD;
    IF B1 THEN EXIT FI OD
end{program}

A Reverse Engineering Example.

Here's the original program:

egin{program}
 VAR seq{m := 0, p := 0, |last| := `` ''}; 
 ACTIONS |prog|: 
|prog| ACTIONEQ %
    seq{|line| := `` '', m := 0, i := 1};
    CALL |inhere| ENDACTION
l ACTIONEQ %
    i := i+1; 
    IF (i=(n+1)) THEN CALL |alldone| FI ; 
    m := 1; 
    IF |item|[i] 
eq |last|
        THEN |write|(|line|); |line| := `` ''; m := 0;
              CALL |inhere| FI ; 
    CALL |more| ENDACTION
|inhere| ACTIONEQ %
    p := |number|[i]; |line| := |item|[i];
    |line| := |line| concat `` '' concat p;
    CALL |more| ENDACTION
|more| ACTIONEQ %
    IF (m=1) THEN p := |number|[i];
    |line| := |line| concat ``, '' concat p FI ; 
    |last| := |item|[i]; 
    CALL l  ENDACTION  
|alldone| ACTIONEQ |write|(|line|); CALL Z ENDACTION ENDACTIONS END
end{program}

And here's the transformed and corrected version:

egin{program}
seq{|line| := `` '', i := 1};
WHILE i 
eq n+1 DO
  |line| := |item|[i] concat `` '' concat |number|[i]; 
  i := i+1; 
  WHILE i 
eq n+1 AND |item|[i] = |item|[i-1] DO 
    |line| := |line| concat ``, '' concat |number|[i]);
    i := i+1 OD ; 
  |write|(|line|) OD 
end{program}

The package also provides a macro for typesetting a set like this: set{x in N | x > 0}.

Lines can be numbered by setting NumberProgramstrue and numbering turned off with NumberProgramsfalse

Package page

Package documentation

The `algorithm` environment[edit]

It is often useful for the algorithm produced by algorithmic to be "floated" to the optimal point in the document to avoid it being split across pages. The algorithm environment provides this and a few other useful features. Include it by adding the
usepackage{algorithm} to your document's preamble. It is entered into by

egin{algorithm}
caption{<your caption for this algorithm>}
label{<your label for references later in your document>}
egin{algorithmic}
<algorithmic environment>
end{algorithmic}
end{algorithm}

Algorithm numbering[edit]

The default numbering system for the algorithm package is to number algorithms sequentially. This is often not desirable, particularly in large documents where numbering according to chapter is more appropriate. The numbering of algorithms can be influenced by providing the name of the document component within which numbering should be recommenced. The legal values for this option are: part, chapter, section, subsection, subsubsection or nothing (default). For example:

usepackage[chapter]{algorithm}

List of algorithms[edit]

When you use figures or tables, you can add a list of them close to the table of contents; the algorithm package provides a similar command. Just put

listofalgorithms

anywhere in the document, and LaTeX will print a list of the "algorithm" environments in the document with the corresponding page and the caption.

An example from the manual[edit]

This is an example taken from the manual (official manual, p.14)

egin{algorithm} % enter the algorithm environment
caption{Calculate $y = x^n$} % give the algorithm a caption
label{alg1} % and a label for 
ef{} commands later in the document
egin{algorithmic} % enter the algorithmic environment
    REQUIRE $n geq0vee x 
eq0$
    ENSURE $y = x^n$
    STATE $y Leftarrow1$
    IF{$n < 0$}
        STATE $X Leftarrow1/ x$
        STATE $N Leftarrow-n$
    ELSE
        STATE $X Leftarrow x$
        STATE $N Leftarrow n$
    ENDIF
    WHILE{$N 
eq0$}
        IF{$N$ is even}
            STATE $X Leftarrow X 	imes X$
            STATE $N Leftarrow N /2$
        ELSE[$N$ is odd]
            STATE $y Leftarrow y 	imes X$
            STATE $N Leftarrow N -1$
        ENDIF
    ENDWHILE
end{algorithmic}
end{algorithm}

The official manual is located at: http://mirrors.ctan.org/macros/latex/contrib/algorithms/algorithms.pdf

References[edit]

The official manual for the algorithms package, Rogério Brito (2009), http://mirrors.ctan.org/macros/latex/contrib/algorithms/algorithms.pdf

来源： https://en.wikibooks.org/wiki/LaTeX/Algorithms

https://www.cnblogs.com/piags/archive/2012/11/06/2757683.html

https://www.latex4technics.com/?note=DAIT81