USACO 2.1 Healthy Holsteins

USACO 2.1 Healthy Holsteins

常规的回溯题

#include  < iostream >
#include  < fstream >

using   namespace  std;

ifstream fin( " holstein.in " );
ofstream fout( " holstein.out " );

#ifdef _DEBUG
#define  out cout
#define  in cin
#else
#define  out fout
#define  in fin
#endif

int  data[ 15 ][ 25 ];
int  cur[ 25 ];
int  need[ 25 ];
bool  used[ 15 ];
int  res_cnt  =  INT_MAX;
bool  res[ 25 ]; 
int  cnt  =   0 ;
int  v;
int  g;

void  backtracing( int  depth);

void  solve()
{
   in >> v;

   for ( int  i = 0 ;i < v; ++ i)
       in >> need[i];

   in >> g;
   for ( int  i = 0 ;i < g; ++ i)
       for ( int  j = 0 ;j < v; ++ j)
           in >> data[i][j];

  backtracing( 0 );

   out << res_cnt;

   for ( int  i = 0 ;i < g; ++ i){
       if (res[i])
           out << "   " << i + 1 ;
  }

   out << endl;
       
}

void  add( int  idx)
{
     for ( int  i = 0 ;i < v; ++ i)
        cur[i] += data[idx][i];
}

void  remove( int  idx)
{
     for ( int  i = 0 ;i < v; ++ i)
        cur[i] -= data[idx][i];
}

bool  isok()
{
     for ( int  i = 0 ;i < v; ++ i){
         if (cur[i] < need[i])
             return   false ;
    }

     return   true ;
}

void  backtracing( int  depth)
{   

     // 剪枝
    if ( cnt >= res_cnt )  return ;


     if (isok()){
         if (cnt < res_cnt){
            res_cnt  =  cnt;
            memcpy(res,used, sizeof (used));
        }
         return ;
    }
 
     if (depth >= g)  return ;

    add(depth);
    used[depth] = true ;
    cnt ++ ;

    backtracing(depth + 1 );

    remove(depth);
    used[depth] = false ;
    cnt -- ;

    backtracing(depth + 1 );
}

int  main( int  argc, char   * argv[])
{
    solve(); 
     return   0 ;
}

Compiling...
Compile: OK

Executing...
 Test 1: TEST OK [0.000 secs, 2844 KB]
 Test 2: TEST OK [0.011 secs, 2840 KB]
 Test 3: TEST OK [0.011 secs, 2844 KB]
 Test 4: TEST OK [0.022 secs, 2840 KB]
 Test 5: TEST OK [0.000 secs, 2844 KB]
 Test 6: TEST OK [0.011 secs, 2844 KB]
 Test 7: TEST OK [0.011 secs, 2840 KB]
 Test 8: TEST OK [0.022 secs, 2844 KB]
 Test 9: TEST OK [0.022 secs, 2840 KB]
 Test 10: TEST OK [0.022 secs, 2840 KB]

All tests OK.