UVa 539 The Settlers of Catan

UVa 539 The Settlers of Catan

果搜即可。
从一个起点开始出发，尝试每条没有走过的边，直到不能走为止。
注意到和顶点数相比，边数要少得多，所以使用邻接表存储。
以下是我的代码：

#include < list >
#include < cstdio >
#include < cstring >
using   namespace  std;
const   int  kMaxn( 27 );


int  n,m,ans;
list < int >  g[kMaxn];
bool  used[kMaxn][kMaxn];

void  dfs( int  node, int  length)
{
     if (ans < length)
        ans = length;
     for (list < int > ::iterator i = g[node].begin();i != g[node].end();i ++ )
         if ( ! used[node][ * i])
        {
            used[node][ * i] = used[ * i][node] = true ;
            dfs( * i,length + 1 );
            used[node][ * i] = used[ * i][node] = false ;
        }
}

int  main()
{
    #ifndef ONLINE_JUDGE
    freopen( " data.in " , " r " ,stdin);
    freopen( " data.out " , " w " ,stdout);
     #endif

     while (scanf( " %d%d " , & n, & m) == 2   &&  (n  ||  m))
    {
         for ( int  i = 0 ;i < n;i ++ )
            g[i].clear();
         for ( int  i = 0 ;i < m;i ++ )
        {
             int  u,v;
            scanf( " %d%d " , & u, & v);
            g[u].push_back(v);
            g[v].push_back(u);
        }

        ans = 0 ;
         for ( int  i = 0 ;i < n;i ++ )
        {
            memset(used, false ,kMaxn * kMaxn * sizeof ( bool ));
            dfs(i, 0 );
        }

        printf( " %d\n " ,ans);
    }

     return   0 ;
}