最大子段和（分而治之求解）

#include<iostream>
#include<vector>
 
using namespace std;
const int Min=-99999;
void MaxSum(const vector<int>&v,int &besti,int &bestj,int& sum,int low,int high)
{
       int i;
       if(low==high) //当low==high,递归截止,sum存放一个元素和
       {
              sum=v[low];
              return;
       }
       else if(low<high) //当low<high,产生递归
       {
              int mid=(low+high)/2; //mid是low...high区间的中值
              int lsum;
              MaxSum(v,besti,bestj,lsum,low,mid); //左区间递归,求low...mid区间最大子段和
              int rsum;
              MaxSum(v,besti,bestj,rsum,mid+1,high);//右区间递归,求mid+1...high区间最大子段和
              //最大子段和可能出现在i...j中,low<=i<=mid, mid<j<=high
              int lbestsum=Min; //lbestsum是i...mid区间最大子段和
              int s=0; //s用于求和
              int L_index; //L_index...mid区间是最大子段和区间
              for(i=mid;i>=low;i--) //求i...mid区间最大子段和
              {
                     s+=v[i];
                     if(s>lbestsum)
                     {
                            L_index=i;
                            lbestsum=s;
                     }
              }
              int rbestsum=Min; //rbestsum是mid+1...high区间最大子段和
              s=0;
              int R_index; //mid_1...R_index区间是最大子段和区间
              for(i=mid+1;i<=high;i++)
              {
                     s+=v[i];
                     if(s>rbestsum)
                     {
                            R_index=i;
                            rbestsum=s;
                     }
              }
              if(lsum>rsum && lsum>(lbestsum+rbestsum)) //最大子段和是出现在low...mid区间内
              {
                     besti=low;
                     bestj=mid;
                     sum=lsum;
              }
              else if(rsum>lsum && rsum>(lbestsum+rbestsum)) //最大子段和是出现在mid+1...high区间内
              {
                     besti=mid+1;
                     bestj=high;
                     sum=rsum;
              }
              else
              {
                     besti=L_index;
                     bestj=R_index;
                     sum=lbestsum+rbestsum;
              }
       }
}
 
void main()
{
       vector<int>v;
       int i,j,sum;
       sum=0;
       int e;
       const int end=-9999;
       cin>>e;
       while(e!=end)
       {
              v.push_back(e);
              cin>>e;
       }
       for(i=0;i<v.size();i++) cout<<i<<":"<<v[i]<<endl;
       MaxSum(v,i,j,sum,0,v.size()-1);
       cout<<"最大子段和从位置"<<i<<"到"<<"位置"<<j<<endl;
       cout<<"最大子段和是:"<<sum<<endl;
}