POJ 2488 A Knight's Journey

POJ 2488 A Knight's Journey

经典搜索问题。
以下是我的代码：

/*
 * Author:  lee1r
 * Created Time:  2011/8/6 7:47:26
 * File Name: poj2488.cpp
  */
#include < iostream >
#include < sstream >
#include < fstream >
#include < vector >
#include < list >
#include < deque >
#include < queue >
#include < stack >
#include < map >
#include < set >
#include < bitset >
#include < algorithm >
#include < cstdio >
#include < cstdlib >
#include < cstring >
#include < cctype >
#include < cmath >
#include < ctime >
#define  L(x) ((x)<<1)
#define  R(x) (((x)<<1)+1)
#define  Half(x) ((x)>>1)
#define  lowbit(x) ((x)&(-(x)))
using   namespace  std;
const   int  kInf( 0x7f7f7f7f );
const   double  kEps(1e - 8 );
typedef  long   long  int64;
typedef unsigned  long   long  uint64;

const   int  kMaxn( 27 );
const   int  dx[] = { - 2 , - 2 , - 1 , 1 , 2 , 2 , 1 , - 1 },dy[] = { - 1 , 1 , 2 , 2 , 1 , - 1 , - 2 , - 2 };

int  n,m;
string  ans,d;
bool  used[kMaxn][kMaxn];

string  itoa( int  x)
{
     string  re,t;
     while (x > 0 )
    {
        t += (x % 10 + ' 0 ' );
        x /= 10 ;
    }
     for ( int  i = t.size() - 1 ;i >= 0 ;i -- )
        re += t[i];
     return  re;
}

void  erase( string   & t)
{
     int  pos;
     for (pos = t.size() - 1 ;pos >= 0 ;pos -- )
         if (isalpha(t[pos]))
             break ;
    t.erase(pos,t.size() - pos);
}

void  dfs( int  depth, int  x, int  y)
{
     if (ans <= d)
         return ;
     if (depth > n * m)
    {
        ans = d;
         return ;
    }
     for ( int  i = 0 ;i < 8 ;i ++ )
    {
         int  newx(x + dx[i]),newy(y + dy[i]);
         if (newx < 1   ||  newx > n  ||  newy < 1   ||  newy > m  ||  used[newx][newy])
             continue ;
        d += ( char )(newx + ' A ' - 1 );
        d += itoa(newy);
        used[newx][newy] = true ;
        dfs(depth + 1 ,newx,newy);
        erase(d);
        used[newx][newy] = false ;
    }
}

int  main()
{
     // freopen("data.in","r",stdin);
    
     int  T;
    scanf( " %d " , & T);
     for ( int  case_num = 1 ;case_num <= T;case_num ++ )
    {
        scanf( " %d%d " , & m, & n);
        ans = " z " ;
         for ( int  i = 1 ;i <= min(Half(n) + 1 ,n);i ++ )
             for ( int  j = 1 ;j <= min(Half(m) + 1 ,m);j ++ )
            {
                d += ( char )(i + ' A ' - 1 );
                d += itoa(j);
                used[i][j] = true ;
                dfs( 2 ,i,j);
                erase(d);
                used[i][j] = false ;
            }
        
        printf( " Scenario #%d:\n " ,case_num);
         if (ans < " z " )
            cout << ans << endl;
         else
            cout << " impossible " << endl;
        cout << endl;
    }
    
     return   0 ;
}