优化拔河比赛队伍分配算法：体重均衡与实力相当

  #include<iostream>      
  using namespace std;      
       
  class Selecting{      
      friend int BestSelecting(int [],int ,int);      
  private:      
      void BacktrackEven(int i);   //总人数为偶数      
      void BacktrackOdd(int i);    //总人数为奇数      
      int n;        //总人数      
      int * w,      //队员体重数组      
          bound,    //较小体重队伍的总体重上界，为总体重的一半      
          cw,       //当前选出的队伍重量      
          bestw,    //选择队伍的最佳重量      
          count;    //选出队伍人数      
  };      
       
  void Selecting::BacktrackEven(int i)      
  {      
      if(i>n){    // 到达叶节点      
          if(cw>bestw && (n/2==count)) bestw = cw;      
              return;      
      }      
       
      if(cw+w[i]<=bound  && count+1<=n/2)      
      {      
          cw+=w[i];      
          count++;      
          BacktrackEven(i+1);      
          cw-=w[i];      
          count--;      

      }      
      BacktrackEven(i+1);      
  }      
       
  void Selecting::BacktrackOdd(int i)      
  {      
      if(i>n){   // 到达叶节点      
          if(cw>bestw && (n/2==count || (n+1)/2==count)) bestw = cw;      
              return;      
      }      
       
      if(cw+w[i]<=bound  && count<=n/2)      
      {      
          cw+=w[i];      
          count++;      
          BacktrackOdd(i+1);      
          cw-=w[i];      
          count--;      
      }      
      BacktrackOdd(i+1);      
  }      
       
  int BestSelecting(int w[],int bound,int n)      
  {      
      Selecting X;      
      X.w = w;      
      X.bound = bound;      
      X.n = n;      
      X.bestw = 0;      
      X.cw = 0;