📄 shuffle.html
字号:
<!DOCTYPE HTML PUBLIC "-//W3O//DTD W3 HTML 2.0//EN"><!-- This collection of hypertext pages is Copyright 1995-2005 by Steve Summit. --><!-- Content from the book "C Programming FAQs: Frequently Asked Questions" --><!-- (Addison-Wesley, 1995, ISBN 0-201-84519-9) is made available here by --><!-- permission of the author and the publisher as a service to the community. --><!-- It is intended to complement the use of the published text --><!-- and is protected by international copyright laws. --><!-- The on-line content may be accessed freely for personal use --><!-- but may not be published or retransmitted without explicit permission. --><!-- --><!-- this page built Sat Dec 24 21:47:46 2005 by faqproc version 2.7 --><!-- from source file librand.sgml dated Sat Jul 3 13:09:31 2004 --><!-- corresponding to FAQ list version 4.0 --><html><!-- Mirrored from c-faq.com/lib/shuffle.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:58:59 GMT --><head><meta name=GENERATOR content="faqproc"><title>Question 13.19</title><link href="notveryrand.html" rev=precedes><link href="fprand.html" rel=precedes><link href="index.html" rev=subdocument></head><body bgcolor="#ffffff"><a href="notveryrand.html" rev=precedes><img src="../images/buttonleft.gif" alt="prev"></a><a href="index.html" rev=subdocument><img src="../images/buttonup.gif" alt="up"></a><a href="fprand.html" rel=precedes><img src="../images/buttonright.gif" alt="next"></a> <a href="../index-2.html"><img src="../images/buttontop.gif" alt="top/contents"></a><a href="../search.html"><img src="../images/buttonsrch.gif" alt="search"></a><hr><p><!-- qbegin --><h1>comp.lang.c FAQ list<font color=blue>·</font><!-- qtag -->Question 13.19</h1><p><font face=Helvetica size=8 color=blue><b>Q:</b></font>How can I return a sequence of random numberswhich don't repeat at all?</p><p><hr><p><font face=Helvetica size=8 color=blue><b>A:</b></font>What you're looking for is often called a``random permutation'' or``shuffle.''One way is to initialize an array with thevalues to be shuffled,then randomly interchange each of the cells with another onelater in the array:<pre> int a[10], i, nvalues = 10; for(i = 0; i < nvalues; i++) a[i] = i + 1; for(i = 0; i < nvalues-1; i++) { int c = randrange(nvalues-i); int t = a[i]; a[i] = a[i+c]; a[i+c] = t; /* swap */ }</pre>where <TT>randrange(N)</TT> is<TT>rand() / (RAND_MAX/(N) + 1)</TT>or one of the other expressions from question <a href="randrange.html">13.16</a>.</p><p>References:Knuth Sec. 3.4.2 pp. 137-8<br></p><!-- aend --><p><hr><a href="notveryrand.html" rev=precedes><img src="../images/buttonleft.gif" alt="prev"></a><a href="index.html" rev=subdocument><img src="../images/buttonup.gif" alt="up"></a><a href="fprand.html" rel=precedes><img src="../images/buttonright.gif" alt="next"></a> <a href="../questions.html"><img src="../images/buttontop.gif" alt="contents"></a><a href="../search.html"><img src="../images/buttonsrch.gif" alt="search"></a><br><!-- lastfooter --><a href="../about.html">about this FAQ list</a> <a href="../eskimo.html">about eskimo</a> <a href="../search.html">search</a> <a href="../feedback.html">feedback</a> <a href="copyright.html">copyright</a><p>Hosted by<a href="http://www.eskimo.com/"><img src="../../www.eskimo.com/img/link/eskitiny.gif" alt="Eskimo North"></a></body><!-- Mirrored from c-faq.com/lib/shuffle.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:58:59 GMT --></html>⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -