10131 Is Bigger Smarter?

//题目信息http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=1072

//本题主要是用动态规划。参考寂静山林的博客，写的非常详细（http://blog.csdn.net/metaphysis/article/details/6860405），这里只是做个个人随笔记录
//2012/2/28
//accepted
//
#include<iostream>
#include<algorithm>
#include<sstream>
using namespace std;

#define MAXNUM 1000

void backtrack(int index);

class elephant
{
public:
    int index;
    int weight;
    int iq;
    bool operator < (const elephant &other) const
    {
        if(weight!=other.weight)
            return weight<other.weight;
        else return iq>other.iq;
    }
};

elephant elephants[MAXNUM];
int length[MAXNUM];
int parent[MAXNUM];
int main()
{
    int index=0,weight,iq;
    int i,j;
    while(cin>>elephants[index].weight>>elephants[index].iq)
    {
        elephants[index].index=index;
        index++;
    }

    sort(elephants,elephants+index);
    for(i=0;i<index;++i)
    {
        length[i]=1;
        parent[i]=-1;
    }

    int maxLength=0,maxIndex=0;
    for(i=0;i<index;++i)
    {
        int iq=elephants[i].iq;
        int weigth=elephants[i].weight;

        for(j=0;j<i;++j)
        {
            if(elephants[j].weight<weigth && elephants[j].iq>iq)
                if(length[i] <= length[j])
                {
                    length[i]=length[j]+1;
                    parent[i]=j;
                }
        }
        
        if(maxLength<length[i])
        {
             maxLength=length[i];
             maxIndex=i;
        }
    }
    cout<<maxLength<<endl;
    backtrack(maxIndex);
    return 0;
}

void backtrack(int index)
{
     if(parent[index]!=-1)
         backtrack(parent[index]);
     cout<<elephants[index].index+1<<endl;
}

动态规划，回溯法输出解，以及父节点记录的方法。。