You want to visit a strange country. There are n cities in the country. Cities are numbered from 1 to n. The unique way to travel in the country is taking planes. Strangely, in this strange country, for every two cities A and B, there is a flight from A to B or from B to A, but not both. You can start at any city and you can finish your visit in any city you want. You want to visit each city exactly once. Is it possible?
Input
There are multiple test cases. The first line of input is an integer T (0 < T <= 100) indicating the number of test cases. Then T test cases follow. Each test case starts with a line containing an integer n(0 < n <= 100), which is the number of cities. Each of the next n * (n - 1) / 2 lines contains 2 numbers A, B (0 < A, B <= n, A != B), meaning that there is a flight from city A to city B.
Output
For each test case:
Sample Input
3 1 2 1 2 3 1 2 1 3 2 3
Sample Output
1 1 2 1 2 3
这是一个dfs解决的题目，只要搜索下就可以得到想要的结果了
#include <iostream>
using namespace std;
#include <string.h>
int map[111][111];
int vis[111];
int re[111];
int n,flag;
int lu;
void dfs(int a)
{
if(lu==n)
{
flag=1;
return;
}
for(int i=1;i<=n;i++)
{
if(!vis[i]&&map[a][i])
{
re[lu]=i;
lu++;
vis[i]=1;
dfs(i);
if(flag)return;
vis[i]=0;
lu--;
}
}
return;
}
int main()
{
int t;
cin>>t;
while (t--) {
cin>>n;
if(n==1)
cout<<1<<endl;
else
{
memset(map, 0, sizeof(map));
memset(re, 0, sizeof(re));
memset(vis, 0, sizeof(vis));
flag=0;
for(int i=0;i<n*(n-1)/2;i++)
{
int s,d;
cin>>s>>d;
map[s][d]=1;
}
for(int i=1;i<=n;i++)
{
lu=0;
re[lu]=i;
lu++;
vis[i]=1;
dfs(i);
lu--;
if(flag)break;
vis[i]=0;
}
if(flag)
{
for(int i=0;i<n;i++)
{
if(i)
cout<<" "<<re[i];
else
cout<<re[i];
}
cout<<endl;
}
else
cout<<"Impossible"<<endl;
}
}
return 0;
}
原文：http://www.cnblogs.com/Annetree/p/6362815.html