题目链接： http://codeforces.com/contest/501/problem/B
The first line contains integer q (1?≤?q?≤?1000), the number of handle change requests.
Next q lines contain the descriptions of the requests, one per line.
Each query consists of two non-empty strings old andnew, separated by a space. The strings consist of lowercase and uppercase Latin letters and digits. Stringsold and new are distinct. The lengths of the strings do not exceed20.
The requests are given chronologically. In other words, by the moment of a query there is a single person with handleold, and handle new is not used and has not been used by anyone.
In the first line output the integer n — the number of users that changed their handles at least once.
In the next n lines print the mapping between the old and the new handles of the users. Each of them must contain two strings,old and new, separated by a space, meaning that before the user had handleold, and after all the requests are completed, his handle isnew. You may output lines in any order.
Each user who changes the handle must occur exactly once in this description.
<pre>5 Misha ILoveCodeforces Vasya Petrov Petrov VasyaPetrov123 ILoveCodeforces MikeMirzayanov Petya Ivanov
3 Petya Ivanov Misha MikeMirzayanov Vasya VasyaPetrov123
#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
using namespace std;
const int maxn=1005;
int main()
{
string Name1[maxn],Name2[maxn];
string s1,s2;
int m;
cin>>m;
int cnt=0;
while(m--)
{
cin>>s1>>s2;
int gg=0;
for(int i=1;i<=cnt;i++)
if(s1==Name2[i])
{
gg=i;
break;
}
if(!gg)
{
Name1[++cnt]=s1;
Name2[cnt]=s2;
continue;
}
Name2[gg]=s2;
}
printf("%d\n",cnt);
for(int i=1;i<=cnt;i++)
cout<<Name1[i]<<" "<<Name2[i]<<endl;
return 0;
}
codeforce B. Misha and Changing Handles
原文：http://blog.csdn.net/u013514722/article/details/42677195