How to write a Pseudo Code

怎样去用伪代码描述一个算法是很重要的，下面是一些推荐的标准。

伪代码是一种用于描述算法的结构化语言。它允许设计者专注于算法的逻辑，而不会被语言语法的细节所分散。同时，伪代码需要完整，它描述算法的整个逻辑，使得实现变成了一种机械的逐行翻译成源代码的任务。

concise: In general the vocabulary used in the pseudocode should be the vocabulary of the problem domain, not of the implementation domain. The pseudocode is a narrative for someone who knows the requirements (problem domain) and is trying to learn how the solution is organized. 可以假设你在向一个不会编程的人描述你实现某个算法的过程。

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Extract the next word from the line (good)
set word to get next token (poor)

Append the file extension to the name (good)
name = name + extension (poor)

FOR all the characters in the name (good)
FOR character = first to last (ok)

fine-grained: Note that the logic must be decomposed to the level of a single loop or decision. Thus “Search the list and find the customer with highest balance” is too vague because it takes a loop AND a nested decision to implement it.
Use mathematical notation when applicable.
structured: The “structured” part of pseudocode is a notation for representing six specific structured programming constructs: SEQUENCE, WHILE, IF-THEN-ELSE, REPEAT-UNTIL, FOR, and CASE.

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**SEQUENCE** is a linear progression where one task is performed sequentially after another.
**WHILE** is a loop (repetition) with a simple conditional test at its **beginning**.
**IF-THEN-ELSE** is a decision (selection) in which a choice is made between two alternative courses of action.
**REPEAT-UNTIL** is a loop with a simple conditional test at the **bottom**.
**CASE** is a multiway branch (decision) based on the value of an expression. CASE is a generalization of IF-THEN-ELSE.
**FOR** is a "counting" loop.

# SEQUENCE
all actions aligned with the same indent

# IF-THEN-ELSE
IF HoursWorked > NormalMax THEN
    Display overtime message
ELSE
    Display regular time message
ENDIF

# WHILE
WHILE Population < Limit
    Compute Population as Population + Births - Deaths
ENDWHILE

# CASE
CASE grade OF
    A : points = 4
    B : points = 3
    C : points = 2
    D : points = 1
    F : points = 0
    others : points = -1
ENDCASE

# REPEAT-UNTIL
REPEAT
    sequence
UNTIL condition

# FOR
FOR each month of the year (good)
FOR month = 1 to 12 (ok)
FOR each employee in the list (good)
FOR empno = 1 to listsize (ok)

FOR each month of the year
    sequence
ENDFOR

-----------------------------------

#  INVOKING SUBPROCEDURES

Use the CALL keyword. For example:

CALL AvgAge with StudentAges
CALL Swap with CurrentItem and TargetItem
CALL Account.debit with CheckAmount
CALL getBalance RETURNING aBalance
CALL SquareRoot with orbitHeight RETURNING nominalOrbit

“Pretty Good” This example shows how pseudocode is written as comments in the source file.

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public boolean moveRobot (Robot aRobot)
{
    //IF robot has no obstacle in front THEN
        // Call Move robot
        // Add the move command to the command history
        // RETURN true
    //ELSE
        // RETURN false without moving the robot
    //END IF
}