北大OJ_1010题：STAMPS

#include <iostream>
#include <vector>
#include <algorithm>


using namespace std;


typedef vector<int> IntArray;

#define   MAX_STAMP_N       4   //最大邮票数
#define   MAX_TYPE_N        25    //最大邮票种类数25

struct tagResultHelper
{
  int nCurTypeCount;        //当前种类数
  int nCurStampCount;       //当前邮票数
  int nCurMaxValue;       //当前最大面额

  int mResultSets[MAX_STAMP_N]; //当前结果集（始终保存最优的结果集）
  bool bTieFlag;          //tie标记
};

tagResultHelper gResultHelper;  //结果集合辅助变量
int gStampArray[MAX_TYPE_N];  //邮票种类数组（保存每种面值）
int gTotalTypeCount;      //总的邮票种类数



//得到最大值
int GetMaxValue( int mIntArray[MAX_STAMP_N], int nCurCount )
{
  int nMax = -1;
  for( int i = 0; i < nCurCount; ++i )
  {
    if ( mIntArray[i] > nMax )
    {
      nMax = mIntArray[i];
    }
  }

  return nMax;
}




//更新最优解
void UpdateBestResult( int nCurTypeCount, int nCurMaxValue, int nCurStampCount,
            int mIntArray[MAX_STAMP_N] )
{
  //种类多于当前的，加入
  if ( nCurTypeCount > gResultHelper.nCurTypeCount )
  {
    gResultHelper.nCurTypeCount = nCurTypeCount;
    gResultHelper.nCurStampCount = nCurStampCount;
    gResultHelper.nCurMaxValue = nCurMaxValue;

    //更新结果
    gResultHelper.bTieFlag = false;//重置tie标记
    for( int i = 0; i < nCurStampCount; ++i ) gResultHelper.mResultSets[i]=mIntArray[i];

  }
  //种类等于当前的
  else if ( nCurTypeCount == gResultHelper.nCurTypeCount )
  {
    //邮票数目小于当前的
    if( nCurStampCount < gResultHelper.nCurStampCount )
    {
      gResultHelper.nCurTypeCount = nCurTypeCount;
      gResultHelper.nCurStampCount = nCurStampCount;
      gResultHelper.nCurMaxValue = nCurMaxValue;

      //更新结果
      gResultHelper.bTieFlag = false;//重置tie标记
      for( int i = 0; i < nCurStampCount; ++i ) gResultHelper.mResultSets[i]=mIntArray[i];
    }
    //邮票数目等于当前的
    else if ( nCurStampCount == gResultHelper.nCurStampCount )
    {
      //单张面值最大的大于当前的
      if ( nCurMaxValue > gResultHelper.nCurMaxValue )
      {
        gResultHelper.nCurTypeCount = nCurTypeCount;
        gResultHelper.nCurStampCount = nCurStampCount;
        gResultHelper.nCurMaxValue = nCurMaxValue;

        //更新结果
        gResultHelper.bTieFlag = false;//重置tie标记
        for( int i = 0; i < nCurStampCount; ++i ) gResultHelper.mResultSets[i]=mIntArray[i];
      }
      //单张面值最大的等于当前的
      else if ( nCurMaxValue == gResultHelper.nCurMaxValue )
      {
        if ( !gResultHelper.bTieFlag )
        {
          for( int i = 0; i < nCurStampCount; ++i ) gResultHelper.mResultSets[i]=mIntArray[i];
          gResultHelper.bTieFlag = true;//已经tie了
        }
      }
    }
  }
}


void GetResult_DFS( int mDstArrayTemp[], int& nCurStampCount, int& nCurTypeCount, int nTarget, int iStart )
{
  if ( nTarget < 0 ) return;
  if ( nTarget == 0 )
  {
    //找到一组结果
    UpdateBestResult( nCurTypeCount, GetMaxValue( mDstArrayTemp, nCurStampCount ), 
      nCurStampCount, mDstArrayTemp );

  }
  else
  {
    for( int i = iStart; i < gTotalTypeCount; ++i )
    {
      //后面更大的数不可能满足条件或者邮票数已经是4张，不能容纳更多了（剪枝操作）
      if( gStampArray[i] > nTarget || nCurStampCount >= 4 ) break;

      //种类数递增
      if ( i > iStart || nCurStampCount <= 0 )
      {
        ++nCurTypeCount;
      }
      mDstArrayTemp[nCurStampCount++] = gStampArray[i];

      //因为可以重复使用，所以可继续从当前位置递归
      GetResult_DFS( mDstArrayTemp, nCurStampCount, nCurTypeCount, nTarget-gStampArray[i], i );

      //重置，即回溯操作
      if ( i > iStart || nCurStampCount == 1 )
      {
        --nCurTypeCount;
      }
      nCurStampCount--;

    }
  }
}



//回溯法
int main()
{
  IntArray customerVec;

  while ( true )
  {
    int nTemp = 0;
    int type[MAX_TYPE_N] = {0};  //面值为i的邮票的种数type[i] 
    gTotalTypeCount = 0;
    //while( cin >> nTemp )
    while( true )
    {
      if ( scanf("%d", &nTemp ) == EOF ) exit(0);

      if ( 0 == nTemp || gTotalTypeCount == MAX_TYPE_N ) break;
      //gStampArray[gTotalTypeCount++] = nTemp;

      if( type[nTemp-1] < 5 )     //剪枝，同面额的邮票种类超过5，则按5计算  
      {  
        type[nTemp-1]++;  
        gStampArray[gTotalTypeCount++] = nTemp;
      }

    }
    sort( gStampArray, gStampArray+gTotalTypeCount );


    customerVec.clear();
    while( cin >> nTemp )
    {
      if ( 0 == nTemp ) break;
      customerVec.push_back( nTemp );
    }


    for( int i = 0; i < customerVec.size(); ++i )
    {
      int iCurTypeCount = 0;
      int iCurStampCount = 0;
      int mDstVecTemp[MAX_STAMP_N];
      memset( mDstVecTemp, 0, sizeof(mDstVecTemp) );
      gResultHelper.nCurMaxValue = 0;
      gResultHelper.nCurStampCount = 0;
      gResultHelper.nCurTypeCount = 0;
      gResultHelper.bTieFlag = false;
      memset( gResultHelper.mResultSets, 0, sizeof(gResultHelper.mResultSets) );

      GetResult_DFS( mDstVecTemp, iCurStampCount, iCurTypeCount, customerVec[i], 0 );


      if ( gResultHelper.nCurTypeCount <= 0 )
      {
        cout << customerVec[i] << " ---- none" << endl;
      }
      else if ( gResultHelper.bTieFlag )
      {
        cout << customerVec[i] << " (" << gResultHelper.nCurTypeCount << "): tie" << endl;
      }
      else
      {
        cout << customerVec[i] << " (" << gResultHelper.nCurTypeCount << "):";
        for( int k = 0; k < gResultHelper.nCurStampCount; ++k )
        {
          cout << " " << gResultHelper.mResultSets[k];
        }
        cout << endl;
      }
    }

  }

  return 0;
}

作者：山丘儿