题目链接:http://codeforces.com/problemset/problem/510/C

Fox Ciel is going to publish a paper on FOCS (Foxes Operated Computer Systems, pronounce: "Fox"). She heard a rumor: the authors list on the paper is always sorted in the lexicographical order.

After checking some examples, she found out that sometimes it wasn't true. On some papers authors' names weren't sorted in lexicographical order in normal sense. But it was always true that after some modification of the order of letters in alphabet, the order of authors becomes lexicographical!

She wants to know, if there exists an order of letters in Latin alphabet such that the names on the paper she is submitting are following in the lexicographical order. If so, you should find out any such order.

Lexicographical order is defined in following way. When we compare s and t, first we find the leftmost position with differing characters: si ≠ ti. If there is no such position (i. e. s is a prefix of t or vice versa) the shortest string is less. Otherwise, we compare characters si and ti according to their order in alphabet.

Input
The first line contains an integer n ( ≤ n ≤ ): number of names. Each of the following n lines contain one string namei ( ≤ |namei| ≤ ), the i-th name. Each name contains only lowercase Latin letters. All names are different. Output
If there exists such order of letters that the given names are sorted lexicographically, output any such order as a permutation of characters 'a'–'z' (i. e. first output the first letter of the modified alphabet, then the second, and so on). Otherwise output a single word "Impossible" (without quotes). Examples
input rivest
shamir
adleman
output
bcdefghijklmnopqrsatuvwxyz
input tourist
petr
wjmzbmr
yeputons
vepifanov
scottwu
oooooooooooooooo
subscriber
rowdark
tankengineer
output
Impossible
input petr
egor
endagorion
feferivan
ilovetanyaromanova
kostka
dmitriyh
maratsnowbear
bredorjaguarturnik
cgyforever
output
aghjlnopefikdmbcqrstuvwxyz
input car
care
careful
carefully
becarefuldontforgetsomething
otherwiseyouwillbehacked
goodluck
output
acbdefhijklmnogpqrstuvwxyz

题意:给出几个排序好的字符串,输出字符串的排序规则,如没有输出  Impossible

#include <cstring>
#include <cstdlib>
#include <cstdio>
#include <math.h>
#include <algorithm>
#include <queue>
using namespace std; #define met(a,b) memset(a,b,sizeof(a))
#define ll long long
#define N 123
struct node
{
int v,next;
}s[N];
int a[N],num[N],vis[N],k;
int len[N],in[N];
void add(int u,int v)
{
s[k].v=u;
s[k].next=a[v];
a[v]=k++;
in[u]++;
}
char str[N][N]; int main()
{
int n;
scanf("%d",&n);met(a,-);k=;
for(int i=;i<n;i++)
{
scanf("%s",str[i]);
len[i]=strlen(str[i]);
}
met(in,);int j;
for(int i=;i<n;i++)
{
for(j=;j<min(len[i],len[i-]);j++)
{
if(str[i][j]!=str[i-][j])///两个字符串的相同位置比较
{
int x=str[i][j]-'a';
int y=str[i-][j]-'a';
add(x,y);
break;
}
}
if(len[i]<len[i-] && j==len[i])///前一个字符串比后一个长,输出不可能
{
printf("Impossible\n");
return ; }
}
met(vis,);
for(int i=;i<=;i++)
{
int jj=;
int j;
for(int j=;j<;j++)///一个一个字符查找符合的
{
if(!vis[j] && in[j]==)
{
vis[j]=;
num[i]=j;
for(int k=a[j];k!=-;k=s[k].next)
in[s[k].v]--; jj=j;
break;
}
}
if(jj==)///中间有断开的,有一个字符没有比较
{
printf("Impossible\n");
return ;
}
}
for(int i=;i<=;i++)
printf("%c",num[i]+'a');
puts(""); return ;
}

(CodeForces 510C) Fox And Names 拓扑排序的更多相关文章

  1. CodeForces 510C Fox And Names (拓扑排序)

    <题目链接> 题目大意: 给你一些只由小写字母组成的字符串,现在按一定顺序给出这些字符串,问你怎样从重排字典序,使得这些字符串按字典序排序后的顺序如题目所给的顺序相同. 解题分析:本题想到 ...

  2. [CF #290-C] Fox And Names (拓扑排序)

    题目链接:http://codeforces.com/contest/510/problem/C 题目大意:构造一个字母表,使得按照你的字母表能够满足输入的是按照字典序排下来. 递归建图:竖着切下来, ...

  3. CF Fox And Names (拓扑排序)

    Fox And Names time limit per test 2 seconds memory limit per test 256 megabytes input standard input ...

  4. CF510C Fox And Names——拓扑排序练习

    省委代码: #include<cstdio> #include<cstdlib> #include<cstring> #include<cmath> # ...

  5. codeforce 510C Fox And Names(拓扑排序)

    Fox And Names time limit per test 2 seconds memory limit per test 256 megabytes input standard input ...

  6. Codeforces Round #290 (Div. 2) 拓扑排序

    C. Fox And Names time limit per test 2 seconds memory limit per test 256 megabytes input standard in ...

  7. CodeForces 909E Coprocessor(无脑拓扑排序)

    You are given a program you want to execute as a set of tasks organized in a dependency graph. The d ...

  8. codeforces 915D Almost Acyclic Graph 拓扑排序

    大意:给出一个有向图,问能否在只去掉一条边的情况下破掉所有的环 解析:最直接的是枚举每个边,将其禁用,然后在图中找环,如果可以就YES,都不行就NO 复杂度O(N*M)看起来不超时 但是实现了以后发现 ...

  9. Codeforces 919D:Substring(拓扑排序+DP)

    D. Substring time limit: per test3 seconds memory limit: per test256 megabytes inputstandard: input ...

随机推荐

  1. 利用Chrome模拟访问移动端网页

    很多网站都通过User-Agent来判断浏览器类型,如果是3G手机,显示手机页面内容,如果是普通浏览器,显示普通网页内容. 谷歌Chrome浏览器,可以很方便地用来当3G手机模拟器.在Windows的 ...

  2. 今天升级了ADT到ADT 22.6.1,打包混淆的时候就出现了问题

    Proguard returned with error code 1. See console Error: Unable to access jarfile ..\lib\proguard.jar ...

  3. IOS开发之——颜色设置

    颜色设置: 指定RGB,參数是:红.绿.黄.透明度,范围是0-1 + (UIColor *)colorWithRed:(CGFloat)red green:(CGFloat)green blue:(C ...

  4. flash builder 4.7 debug via usb device iPhone 4s - device not found

    http://forums.adobe.com/message/4865192 Please provide more info on the above issue: 1.What is the m ...

  5. cocos2d-x引擎实现$1Unistroke Recognizer手势识别

    $1 Unistroke(单笔画) Recognizer官网 http://depts.washington.edu/aimgroup/proj/dollar/ (在官网还有多笔画的识别库) 代码下载 ...

  6. python列表删除重复元素的三种方法

    给定一个列表,要求删除列表中重复元素. listA = ['python','语','言','是','一','门','动','态','语','言'] 方法1,对列表调用排序,从末尾依次比较相邻两个元素 ...

  7. CSS 之 清除 float 常用的方法

    大多数前端使用.clearfix:after{ .....}  和 .clearit{....}的组合来清除浮动. 前端开发经常用到浮动 float:left; float:right; 有浮动就需要 ...

  8. ubuntu 13.04 root权限设置方法详解

    很多朋友安装升级Ubuntu 13.04之后不知道ubuntu 13.04 root权限设置的具体方法,今天这篇文章就将为大家详细介绍设置root权限的步骤,新手朋友可以来看一看哦~ Ubunto 1 ...

  9. MySQL(1):启动MySQL服务,客户端连接服务

    1.安装完毕mysql之后,在windows中找到服务,启动MySQL服务(服务端)(mysqld.exe) 2.接下来启动客户端(mysql.exe) 这里参数中: -hlocalhost 表示主机 ...

  10. Adroid_Spinner_ArrayAdapter

    XML布局文件 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmln ...