📄 2039 -- to and fro.htm
字号:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<!-- saved from url=(0035)http://poj.grids.cn/problem?id=2039 -->
<HTML><HEAD><TITLE>2039 -- To and Fro</TITLE>
<META http-equiv=Pragma content=no-cache>
<META http-equiv=Content-Type content="text/html; charset=gb2312"><LINK
href="2039 -- To and Fro.files/poj.css" type=text/css rel=stylesheet>
<SCRIPT language=javascript src="2039 -- To and Fro.files/poj.js"></SCRIPT>
<META content="MSHTML 6.00.2900.2180" name=GENERATOR></HEAD>
<BODY vLink=blue aLink=blue link=blue leftMargin=5><A name=top></A>
<TABLE style="BORDER-COLLAPSE: collapse" borderColor=#ffffff width="100%"
border=1>
<TBODY>
<TR>
<TD
style="BACKGROUND-IMAGE: url(images/header.jpg); BACKGROUND-REPEAT: no-repeat; TEXT-ALIGN: right"
vAlign=bottom align=middle colSpan=5 height=160>
<DIV style="MARGIN-BOTTOM: 0px"><IMG
src="2039 -- To and Fro.files/logopku.gif" border=0> <IMG
src="2039 -- To and Fro.files/logo4.gif" border=0></DIV></TD></TR>
<TR vAlign=top align=middle bgColor=#6589d1>
<TH class=h>Online Judge</TH>
<TH class=h>Problem Set</TH>
<TH class=h>Authors</TH>
<TH class=h>Online Contests</TH>
<TH class=h>User</TH></TR>
<TR vAlign=top align=middle bgColor=#f1f1fd>
<TD class=h onmouseover="scbg(this, 1)" onmouseout="scbg(this, 0)"><A
href="http://poj.grids.cn/bbs">Web Board</A><BR><A
href="http://poj.grids.cn/">Home Page</A><BR><A
href="http://poj.grids.cn/faq.htm"
target=_blank>F.A.Qs</A><BR>Announcement</TD>
<TD class=h onmouseover="scbg(this, 1)" onmouseout="scbg(this, 0)">
<FORM action=gotoproblem method=get><A
href="http://poj.grids.cn/problemlist">Problems</A><BR><A
href="http://poj.grids.cn/submit">Submit Problem</A><BR><A
href="http://poj.grids.cn/status">Online Status</A><BR><FONT
color=blue>Prob.ID:</FONT><INPUT size=6 name=pid><INPUT type=submit value=Go name=pb1></FORM></TD>
<TD class=h onmouseover="scbg(this, 1)" onmouseout="scbg(this, 0)">
<FORM action=searchuser method=get><A
href="http://poj.grids.cn/register">Register</A><BR><A
href="http://poj.grids.cn/modifyuser">Update your info</A><BR><A
href="http://poj.grids.cn/userlist">Authors ranklist</A><BR><INPUT size=10
name=key><INPUT type=submit value=Search name=B1></FORM></TD>
<TD class=h onmouseover="scbg(this, 1)" onmouseout="scbg(this, 0)"><FONT
color=#1a5cc8>Current Contest</FONT><BR><A
href="http://poj.grids.cn/pastcontests">Past Contests</A><BR><A
href="http://poj.grids.cn/contests">Scheduled Contests</A><BR><A
href="http://poj.grids.cn/awardcontest_announce.htm" target=_blank><FONT
color=red>Award Contest</FONT></A></TD>
<TD class=h onmouseover="scbg(this, 1)" onmouseout="scbg(this, 0)"
align=left>Welcome<BR><A
href="http://poj.grids.cn/userstatus?user_id=tatalove"
target=_parent><B>tatalove</B></A> <A
href="http://poj.grids.cn/login?action=logout&url=/problem?id=2039">Log
Out</A><BR><A href="http://poj.grids.cn/mail" target=_parent><FONT
color=blue>Mail:0(<B>0</B>)</FONT></A></TD></TR></TBODY></TABLE>
<TABLE width="100%" background="2039 -- To and Fro.files/table_back.jpg"
border=0>
<TBODY>
<TR>
<TD>
<P align=center><FONT color=blue size=5>To and Fro</FONT> <BR>Time
Limit:1000MS Memory Limit:30000K<BR>Total Submit:812 Accepted:569
</P>
<P><FONT color=blue size=5>Description</FONT><BR><FONT
face="Times New Roman" size=3>Mo and Larry have devised a way of
encrypting messages. They first decide secretly on the number of columns
and write the message (letters only) down the columns, padding with extra
random letters so as to make a rectangular array of letters. For example,
if the message is "There’s no place like home on a snowy night" and there
are five columns, Mo would write down <BR><PRE>t o i o y
<BR>h p k n n
<BR>e l e a i
<BR>r a h s g
<BR>e c o n h
<BR>s e m o t
<BR>n l e w x</PRE><BR>Note that Mo includes only letters and writes them
all in lower case. In this example, Mo used the character "x" to pad the
message out to make a rectangle, although he could have used any letter.
<BR><BR>Mo then sends the message to Larry by writing the letters in each
row, alternating left-to-right and right-to-left. So, the above would be
encrypted as <BR><BR>toioynnkpheleaigshareconhtomesnlewx <BR><BR>Your job
is to recover for Larry the original message (along with any extra padding
letters) from the encrypted one. <BR></FONT>
<P></P>
<P><FONT color=blue size=5>Input</FONT><BR><FONT face="Times New Roman"
size=3>There will be multiple input sets. Input for each set will consist
of two lines. The first line will contain an integer in the range 2. . .
20 indicating the number of columns used. The next line is a string of up
to 200 lower case letters. The last input set is followed by a line
containing a single 0, indicating end of input.</FONT></P>
<P><FONT color=blue size=5>Output</FONT><BR><FONT face="Times New Roman"
size=3>Each input set should generate one line of output, giving the
original plaintext message, with no spaces.</FONT></P>
<P><FONT color=blue size=5>Sample Input</FONT><BR><FONT
face="Times New Roman" size=3><PRE>5
toioynnkpheleaigshareconhtomesnlewx
3
ttyohhieneesiaabss
0</PRE></FONT>
<P></P>
<P><FONT color=blue size=5>Sample Output</FONT><BR><FONT
face="Times New Roman" size=3><PRE>theresnoplacelikehomeonasnowynightx
thisistheeasyoneab</PRE></FONT>
<P></P>
<P><FONT color=blue size=5>Source</FONT><BR><FONT face="Times New Roman"
size=3><A
href="http://poj.grids.cn/searchproblem?field=source&key=East Central North America 2004">East
Central North America 2004</A></FONT></P></TD></TR></TBODY></TABLE><FONT
color=#333399 size=3>
<P align=center>[<A
href="http://poj.grids.cn/submit?problem_id=2039">Submit</A>] [<A
href="javascript:history.go(-1)">Go Back</A>] [<A
href="http://poj.grids.cn/problemstatus?problem_id=2039">Status</A>]
[<A href="http://poj.grids.cn/bbs?problem_id=2039">Discuss</A>] </FONT></P>
<P><IMG height=30 src="2039 -- To and Fro.files/home.gif" width=40
border=0><FONT size=3><A href="http://poj.grids.cn/">Home Page</A>
</FONT> <IMG height=30 src="2039 -- To and Fro.files/goback.gif"
width=40 border=0><FONT size=3><A href="javascript:history.go(-1)">Go
Back</A> <IMG height=30 src="2039 -- To and Fro.files/top.gif"
width=40 border=0><A href="http://poj.grids.cn/problem?id=2039#top">To
top</A></FONT><BR>
<HR>
<P style="FONT-FAMILY: Arial," align=center sans-serif Helvetica,>All Rights
Reserved 2003-2006 Ying Fuchen,Xu Pengcheng,Xie Di<BR>Any problem, Please <A
href="mailto:xiedipoj@yahoo.com">Contact Administrator</A></P></BODY></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 + -